Initial Support for a Global "App" class with support for basic common events.
Merge branch 'master' of https://github.com/XForms/XForms-Toolkit

Conflicts:
	samples/XForms.Toolkit.Sample.Droid/MainActivity.cs
	samples/XForms.Toolkit.Sample.WP/App.xaml.cs
	samples/XForms.Toolkit.Sample.iOS/AppDelegate.cs
	samples/XForms.Toolkit.Sample/App.cs