Mostly cleanup of unused code.
Fixed linespacing to use the font metrics.
Removed unused usings.
Simpler conversion to alpha premultiplied greyscale.
Disabled border padding which is causign artifacts.
Use the font height for unrendered characters.
Fix license for all basic types
Add support for multisampled rendertargets in most OpenGL and OpenGLES platforms
Fix mac build
Disable msaa support for MonoMac (for now)
Fixed GL.RenderbufferStorageMultisample not supported in MonoMac
Add PlatformResolveRenderTargets placeholder to all platforms
Fix Monomac msaa support
Merge branch 'develop' of https://github.com/mono/MonoGame into opengl_msaa

Conflicts:
	MonoGame.Framework/Graphics/RenderTarget2D.OpenGL.cs
Merge pull request #2782 from flyingdevelopmentstudio/opengl_msaa

Add support for multisampled rendertargets in most OpenGL platforms
Added Mono.Xna note to License.txt
Fix license
Fix license 2
Merge branch 'develop' into fontsize
Rewrited headers