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
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 full-dxt-support

Conflicts:
	MonoGame.Framework/Graphics/GraphicsExtensions.cs
	MonoGame.Framework/Graphics/Texture2D.cs
	MonoGame.Framework/Graphics/TextureCube.cs
Merge pull request #1662 from slygamer/full-dxt-support

Full support for DXT/S3TC textures
Move device creation back to before ApplyChanges is called.  Along with the PreparingDeviceSettings as well.
Add comment to mod
Merge pull request #1751 from kjpou1/develop

Develop - Fix for Issue #1750 - Move device creation back to before ApplyChanges is called.
Moved the 'WINDOWS || WINRT' endif that was preventing the graphics device from being created.
Merge pull request #1757 from klutch/develop

Moved the 'WINDOWS || WINRT' endif that was preventing the graphics device from being created
Added a call to TextureCollcetion.Dirty() when changing render targets in OpenGL versions.
Merge pull request #1760 from bwfox/PR1758

Fix for issue #1758 - Drawing SpriteFonts to multiple RenderTarget2Ds consecutively leads to all but the first render target missing the text (WindowsGL)