Added Matrix4x3 and Matrix3x4 implementations from our game.
Added very basic implementations of all possible matrix sizes up to 4x4
Moved the indexers out of the Properties region and into their own Indexers region
Matrix2 implementation
Started on Matrix2x3 implementation
Minor changes to Matrix3 and Matrix4
More work on matrices.
Fixed some static fields in the math classes that weren't also readonly.
Matrix2x3 and Matrix2x4 implementatinos
Matrix3x2 implementation and partial Matrix4x2 implementation.
Matrix4x2 implementation and documenting the other matrix classes.
Implemented Matrix3(d) constructor that takes upper-left 3x3 of a Matrix4(d) as discussed in the following issue: https://github.com/andykorth/opentk/issues/4
Copied float matrix classes to their double equivalents.
Converted tabs to spaces.
Added GL.UniformMatrix* double overloads.
Merge branch 'master' of github.com:andykorth/opentk

Conflicts:
	Source/OpenTK/Math/Matrix3.cs
	Source/OpenTK/Math/Matrix3d.cs
minor notes in comments of Matrix classes