Merge pull request #243 from fragmer/master

Fixed a number of issues in TextureSelectionScreen
Fixes #238 and #240
Cleaned up constants and variable names in com.mojang.minecraft.render.Renderer
Renamed MinecraftApplet$1 to MinecraftCanvas
Got rid of a 'this' leak in ParticleManager constructor. Level.particleEngine field is set in Minecraft.setLevel anyway, so this was never needed.