Weather overlays

With VEF you can make new weathers with new custom weather overlays. For example, to add an acidic yellow rain or to add a new fog with a new texture. Example of usage:

<WeatherDef>
  <defName>RG_Monsoon</defName>
  <label>monsoon</label>
  ...
  <overlayClasses>
    <li>VFECore.WeatherOverlay_Custom</li> <!-- overlay class, responsible for drawing overlay. Takes values from VFECore.WeatherOverlayExtension mod extension -->
    <!--<li>VFECore.WeatherOverlay_CustomTwo</li> --> <!-- optional overlay, used only if you want more than one overlay. Takes values from VFECore.WeatherOverlayExtensionTwo mod extension -->
  </overlayClasses>
  ...
  <modExtensions>
    <li Class="VFECore.WeatherOverlayExtension">
      <overlayPath>Weather/CloudyWorldOverlay</overlayPath>            <!-- path to the texture to be used as an overlay -->
      <copyPropertiesFrom>Weather/FogOverlayWorld</copyPropertiesFrom> <!-- the shader properties will be used from this shader -->
        <!-- You can use following shaders: 
          Weather/FogOverlayWorld - to emulate a fog
	  Weather/SnowOverlayWorld - to emulate a snow
	  Weather/RainOverlayWorld - to emulate a rain -->
      <worldPanDir1>(1, 1)</worldPanDir1>                   <!-- first direction to pan into -->
      <worldOverlayPanSpeed1>0.0005</worldOverlayPanSpeed1> <!-- speed of the first direction pan -->
      <worldPanDir2>(1, -1)</worldPanDir2>                  <!-- second direction to pan into -->
      <worldOverlayPanSpeed2>0.0004</worldOverlayPanSpeed2> <!-- speed of the second direction pan -->
    </li>
    <!-- optional extension, used only if you have ReGrowthCore.WeatherOverlay_CustomTwo overlay class in the def
    <li Class="VFECore.WeatherOverlayExtensionTwo">
      <overlayPath>Weather/MonsoonWorldOverlay</overlayPath>
      <copyPropertiesFrom>Weather/RainOverlayWorld</copyPropertiesFrom>
      <worldOverlayPanSpeed1>0.015</worldOverlayPanSpeed1>
      <worldPanDir1>(-0.25, -1)</worldPanDir1>
      <worldOverlayPanSpeed2>0.022</worldOverlayPanSpeed2>
      <worldPanDir2>(-0.24, -1)</worldPanDir2>
    </li>--> 
  </modExtensions>
</WeatherDef>