Optimizations for drawing.

* Game1.cs:
* Renderer.cs:
* Constants.cs:
* wood.png:
* Wall.cs:
* Raycast.Mac.csproj:
* Floor.cs:
* Renderer.cs:
* CastedRay.cs:
* colorstone.png:
* Raycast.Engine.csproj:
* AbstractRenderer.cs:
* Vector2Extensions.cs: 
* Caster.cs: