Added solutions and projects for Android and iOS builds.

Xamarin.iOS and Xamarin.Android are capable of all of the .Net 4.5
features, except for ASYNC_AWAIT for Xamarin.iOS.

Added solutions and projects that enable the compilation constants
needed to build on MonoTouch (Xamarin.iOS) and Mono for Android
(Xamarin.Android).
Added pragmas to avoid warnings.

pragmas added to disable warning 0618 complaining about the use of
deprecated interfaces. Calls were not updated assuming they remain like
that to keep support for .Net 3.5. The pragmas explicitly state that we
are OK with the interfaces being used, despite being marked as
obsoleted.
Samples for Android and iOS.

Taken from dalexsoto's fork. Examples for the core, non-gui stuff. Gui
control code will follow.
Stuff to ignore from Xamarin Studio.