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
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.
Merge branch 'develop' of https://github.com/mono/MonoGame into winrtGuideShowKeyboardInput
Throws NotImplementedException on non-XAML builds
Merge pull request #2250 from mrhlemut/develop

Fix for wrong auto rotation on iOS
Merge pull request #2120 from azchohfi/winrtGuideShowKeyboardInput

Guide.ShowKeyboardInput for WinRT
Merge branch 'develop' of https://github.com/mono/MonoGame into develop