Fixing build issue with Atanh and fixing some build warnings

src/ProjNet/CoordinateSystemServices.cs

@@ -305,6 +305,11 @@ public ICoordinateTransformation CreateTransformation(CoordinateSystem source, C
             return _ctFactory.CreateFromCoordinateSystems(source, target);
         }
 
+        /// <summary>
+        /// AddCoordinateSystem
+        /// </summary>
+        /// <param name="srid"></param>
+        /// <param name="coordinateSystem"></param>
         protected void AddCoordinateSystem(int srid, CoordinateSystem coordinateSystem)
         {
             lock (((IDictionary) _csBySrid).SyncRoot)
@@ -332,6 +337,11 @@ protected void AddCoordinateSystem(int srid, CoordinateSystem coordinateSystem)
             }
         }
 
+        /// <summary>
+        /// AddCoordinateSystem
+        /// </summary>
+        /// <param name="coordinateSystem"></param>
+        /// <returns></returns>
         protected virtual int AddCoordinateSystem(CoordinateSystem coordinateSystem)
         {
             int srid = (int) coordinateSystem.AuthorityCode;
@@ -340,11 +350,17 @@ protected virtual int AddCoordinateSystem(CoordinateSystem coordinateSystem)
             return srid;
         }
 
+        /// <summary>
+        /// Clear
+        /// </summary>
         protected void Clear()
         {
             _csBySrid.Clear();
         }
 
+        /// <summary>
+        /// Count
+        /// </summary>
         protected int Count
         {
             get
@@ -354,11 +370,21 @@ protected int Count
             }
         }
 
+        /// <summary>
+        /// RemoveCoordinateSystem
+        /// </summary>
+        /// <param name="srid"></param>
+        /// <returns></returns>
+        /// <exception cref="NotSupportedException"></exception>
         public bool RemoveCoordinateSystem(int srid)
         {
             throw new NotSupportedException();
         }
 
+        /// <summary>
+        /// GetEnumerator
+        /// </summary>
+        /// <returns></returns>
         public IEnumerator<KeyValuePair<int, CoordinateSystem>> GetEnumerator()
         {
             _initialization.WaitOne();

src/ProjNet/CoordinateSystems/CoordinateSystemFactory.cs

@@ -27,11 +27,8 @@ namespace ProjNet.CoordinateSystems
     /// </summary>
     /// <remarks>
     /// <para>CoordinateSystemFactory allows applications to make coordinate systems that 
-    /// cannot be created by a <see cref="CoordinateSystemAuthorityFactory"/>. This factory is very 
-    /// flexible, whereas the authority factory is easier to use.</para>
-    /// <para>So <see cref="ICoordinateSystemAuthorityFactory"/>can be used to make 'standard' coordinate 
-    /// systems, and <see cref="CoordinateSystemFactory"/> can be used to make 'special' 
-    /// coordinate systems.</para>
+    /// is very flexible, whereas the other factories are easier to use.</para>
+    /// <para>So this Factory can be used to make 'special' coordinate systems.</para>
     /// <para>For example, the EPSG authority has codes for USA state plane coordinate systems 
     /// using the NAD83 datum, but these coordinate systems always use meters. EPSG does not 
     /// have codes for NAD83 state plane coordinate systems that use feet units. This factory

src/ProjNet/CoordinateSystems/Info.cs

@@ -35,7 +35,7 @@ public abstract class Info : IInfo
 		/// were specified in the Simple Features interfaces, so they have been kept here.</para>
 		/// <para>This specification does not dictate what the contents of these items 
 		/// should be. However, the following guidelines are suggested:</para>
-		/// <para>When <see cref="ICoordinateSystemAuthorityFactory"/> is used to create an object, the ‘Authority’
+		/// <para>When <see href="ICoordinateSystemAuthorityFactory"/> is used to create an object, the ‘Authority’
 		/// and 'AuthorityCode' values should be set to the authority name of the factory object, and the authority 
 		/// code supplied by the client, respectively. The other values may or may not be set. (If the authority is 
 		/// EPSG, the implementer may consider using the corresponding metadata values in the EPSG tables.)</para>

src/ProjNet/CoordinateSystems/Projections/MapProjection.cs

@@ -49,10 +49,19 @@ namespace ProjNet.CoordinateSystems.Projections
     [Serializable]
     public abstract class MapProjection : MathTransform, IProjection
     {
+        /// <summary>
+        /// EPS10 => 1e-10.
+        /// </summary>
         protected const double EPS10 = 1e-10;
 
+        /// <summary>
+        /// EPS7 => 1e-7.
+        /// </summary>
         protected const double EPS7 = 1e-7;
 
+        /// <summary>
+        /// HUGE_VAL => double.NaN.
+        /// </summary>
         protected const double HUGE_VAL = double.NaN;
 
         // ReSharper disable InconsistentNaming
@@ -1154,6 +1163,11 @@ protected static double LatitudeToRadians(double y, bool edge)
         private const double P20 = 0.01677689594356261023; /* 761 / 45360 */
 
 
+        /// <summary>
+        /// authset
+        /// </summary>
+        /// <param name="es"></param>
+        /// <returns></returns>
         protected static double[] authset(double es)
         {
             double[] APA = new double[3];
@@ -1169,6 +1183,12 @@ protected static double[] authset(double es)
             return APA;
         }
 
+        /// <summary>
+        /// authlat
+        /// </summary>
+        /// <param name="beta"></param>
+        /// <param name="APA"></param>
+        /// <returns></returns>
         protected static double authlat(double beta, double[] APA)
         {
             double t = beta + beta;

src/ProjNet/CoordinateSystems/Projections/PolarStereographicProjection.cs

@@ -212,7 +212,18 @@ public override MathTransform Inverse()
         private double tsfn(double cosphi, double sinphi, double e)
         {
             double t = (sinphi > 0.0) ? cosphi / (1.0 + sinphi) : (1.0 - sinphi) / cosphi;
-            return Math.Exp(e * Math.Atanh(e * sinphi)) * t;
+            return Math.Exp(e * Atanh(e * sinphi)) * t;
+        }
+
+
+        /// <summary>
+        /// Atanh - Inverse of Math.Tanh
+        /// </summary>
+        /// <remarks>The Math.Atanh is not available for netstandard2.0.</remarks>
+        /// <param name="x"></param>
+        private static double Atanh(double x)
+        {
+            return Math.Log((1 + x) / (1 - x)) * 0.5;
         }
     }
 }

src/ProjNet/CoordinateSystems/Transformations/GeographicTransform.cs

@@ -65,11 +65,17 @@ public override string XML
 			}
 		}
 
+        /// <summary>
+        /// DimSource
+        /// </summary>
         public override int DimSource
         {
             get { return SourceGCS.Dimension; }
         }
 
+        /// <summary>
+        /// DimTarget
+        /// </summary>
         public override int DimTarget
         {
             get { return TargetGCS.Dimension; }

src/ProjNet/CoordinateSystems/VerticalDatum.cs

@@ -24,6 +24,9 @@ public VerticalDatum(DatumType type, string name, string authority, long code, s
         {
         }
 
+        /// <summary>
+        /// ODN - VerticalDatum
+        /// </summary>
         public static VerticalDatum ODN
         {
             get