bug fix (microsoft#1604 & microsoft#1579)

Unity/UnityDemo/Assets/AirSimAssets/Scripts/InitializeAirSim.cs

@@ -50,15 +50,22 @@ public static string GetAirSimSettingsFileName()
         }
 
         fileName = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), Path.Combine("AirSim", "settings.json"));
+        string linuxFileName = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), Path.Combine("Documents/AirSim", "settings.json"));
         Debug.Log(fileName);
+        Debug.Log(linuxFileName);
         if (File.Exists(fileName))
         {
 
             return fileName;
         }
-
+        else if (File.Exists(linuxFileName))
+        {
+            return linuxFileName;
+        }
         if (CreateSettingsFileWithDefaultValues(fileName))
             return fileName;
+        else if (CreateSettingsFileWithDefaultValues(linuxFileName))
+            return linuxFileName;
         else
             return string.Empty;
     }
@@ -68,6 +75,11 @@ public static bool CreateSettingsFileWithDefaultValues(string fileName)
         var result = false;
         try
         {
+            if (fileName.Substring(0, 5) == "/home")
+                Directory.CreateDirectory(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "Documents/AirSim"));
+            else
+                Directory.CreateDirectory(Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.MyDocuments), "AirSim"));
+
             string content = "{\n \"SimMode\" : \"\", \n \"SettingsVersion\" : 1.2, \n \"SeeDocsAt\" : \"https://github.com/Microsoft/AirSim/blob/master/docs/settings.md\"\n}";
             //settings file created at Documents\AirSim with name "setting.json".
             StreamWriter writer = new StreamWriter(File.Open(fileName, FileMode.OpenOrCreate, FileAccess.Write));