Split RenderSprites out of RenderSimple.

RenderSprites handles sprite drawing independently
from the extra bits needed by actors that only use
sprites.

OpenRA.Game/OpenRA.Game.csproj

@@ -225,6 +225,7 @@
     <Compile Include="Network\UPnP.cs" />
     <Compile Include="Widgets\ClientTooltipRegionWidget.cs" />
     <Compile Include="Graphics\Renderable.cs" />
+    <Compile Include="Traits\Render\RenderSprites.cs" />
   </ItemGroup>
   <ItemGroup>
     <ProjectReference Include="..\OpenRA.FileFormats\OpenRA.FileFormats.csproj">