Guide.ShowKeyboardInput for WinRT

I've implemented the Guide.ShowKeyboardInput for WinRT. It uses a XAML
to draw a PopUp with an InputBox (or PasswordBox) and two buttons, one
for OK and other for Cancel. It is similar to the MessageDialog.
Merge branch 'develop' of https://github.com/mono/MonoGame into winrtGuideShowKeyboardInput
Now compiling again on WP8 branch.
Fix for wrong auto rotation on iOS

iOS has inverted LanscapeLeft and LandscapeRight orientation compared to XNA.
While other methods take that in account, it was missing in ToUIInterfaceOrientationMask, which was a potential source of unwanted auto rotation and crashes if the rotation resulted in unsupported Info.plist orientations.

See codeplex discussion for details: https://monogame.codeplex.com/discussions/535677
Added support to load from parent directory using ".." in ContentManager
Support for multiple parent dirs after eachother
Use URI to resolve the path
Merge branch 'develop' of https://github.com/mono/MonoGame into winrtGuideShowKeyboardInput

Conflicts:
	MonoGame.Framework/MonoGame.Framework.Windows8.csproj
	MonoGame.Framework/Windows/GamerServices/Guide.cs

Merged with new Protobuild process.
Replaced licenses.
Replaced #if-#elif logic in default Framework.Media classes.
First run at reorganizing Song.cs and MediaPlayer.cs on a per-API basis.
Merge branch 'develop' into MediaPlayerSplit
Removed iOS code from Song.cs
Removed duplicate methods contained in the Linux path.
Merge branch 'develop' of https://github.com/mono/MonoGame into develop
Merge branch 'develop' of https://github.com/mono/MonoGame into winrtGuideShowKeyboardInput
Support for Texture2D.FromStream on WP8
Fix Android build
Split Video and VideoPlayer files on a per-API basis.
Removed Video from Normalize, as the route of loading raw files through the ContentManager will soon be killed off.
Removed duplicate destructor.
Merge branch 'MediaPlayerSplit' into VideoPlayerSplit