Check in of Single solution projects - from develop branch onlu, no changes reqd

* vs solution - MonoGame.Framework.sln - Manages all windows based solutons

* Xmarin solution - MonoGame.Framework.Xamarin.sln - Manages all solutions supported by Xamaring Studio (Needs Trial or Ent license to build)
Mipmap generation for DXT textures.
Mipmap generation for PVRTC compressed textures.
Fixed crash when changing the value of a processor parameter.
Fixed Dll lookup in MGCB to look in executable path.
Optimized away parameter and pass lookup within SpriteBatch.
Optimized away parameter and pass lookup within SpriteBatch.
Merge branch 'spriteopt' of github.com:SickheadGames/MonoGame into spriteopt
Oops... these don't need to be nulled.
We now use the ref/out Matrix methods in SpriteBatch.
Optimized away extra transform in SpriteBatch under GL.
Merge pull request #1651 from SickheadGames/spriteopt

Simple SpriteBatch Optimizations
Merge branch 'develop' into develop.singlesolution
Merge pull request #1639 from DDReaper/develop.singlesolution

Check in of Single solution projects
Merge pull request #1645 from SickheadGames/GenerateMipmaps

DXT and PVRTC Mipmap Generation