Full support for DXT/S3TC textures
Based on reported extensions for OpenGL, DXT mipmapped textures are now supported by all devices that claim support for the formats.
Merge branch 'develop' of https://github.com/mono/MonoGame into full-dxt-support
Merge branch 'develop' of https://github.com/mono/MonoGame into full-dxt-support

Conflicts:
	MonoGame.Framework/Graphics/GraphicsExtensions.cs
Simplified WP8 trial mode because the Windows 8 style license information is error-prone
Added bitmap content classes for DXT1,3,5.
DxtBitmapContent is now abstract.
Removed DxtBitmapContent.TryGetFormat (implemented by derived classes).
Added Bgr565, Bgra4444, Byte4 packed vector classes to all projects.
Corrected case for DxtBitmapContent, PvrtcBitmapContent.
DxtBitmapContent now matches XNA and C# naming conventions.
PvrtcBitmapContent follows suit.
Second part of rename.
Fix missing abstract keyword.
Fix reference to renamed PvrtcBitmapContent class.
Fixed a bug in the MediaQueue where the active song did not default to -1.
This would cause existing games to think that a song was available already
when it wasn't. The XNA default is -1.
Merge branch 'develop' of https://github.com/mono/MonoGame into develop
Merge branch 'develop' of https://github.com/mono/MonoGame into develop
Merge branch 'develop' of https://github.com/mono/MonoGame into develop
Merge branch 'develop' of https://github.com/mono/MonoGame into develop
Merge branch 'develop' of https://github.com/mono/MonoGame into develop
Merge branch 'develop' of https://github.com/mono/MonoGame into full-dxt-support

Conflicts:
	MonoGame.Framework/Graphics/Texture.cs
Corrected case for DxtBitmapContent, PvrtcBitmapContent.
DxtBitmapContent now matches XNA and C# naming conventions.
PvrtcBitmapContent follows suit.
Second part of rename.
Fix missing abstract keyword.
Fix reference to renamed PvrtcBitmapContent class.
Merge branch 'develop' of https://github.com/mono/MonoGame into develop
Merge branch 'develop' of https://github.com/mono/MonoGame into full-dxt-support

Conflicts:
	MonoGame.Framework/Graphics/GraphicsExtensions.cs
	MonoGame.Framework/Graphics/Texture2D.cs
	MonoGame.Framework/Graphics/TextureCube.cs