Simplify return statements.

Remove redundant ‘this’.
Remove unused using directives.
Simplify LINQ chains.
Add some trait property descriptions.
Add readonly where viable.
Add fullstops to some yaml descriptions.

OpenRA.Mods.TS/SpriteLoaders/TmpTSLoader.cs

@@ -9,11 +9,8 @@
 #endregion
 
 using System;
-using System.Collections.Generic;
 using System.Drawing;
 using System.IO;
-using System.Linq;
-using OpenRA.FileFormats;
 using OpenRA.Graphics;
 
 namespace OpenRA.Mods.TS.SpriteLoaders