[Ide.Tests] Initialize all of xamarin studio!

This initializes nearly all of XS in the 'correct' way. We have
a full IdeApp and all the misc stuff has been initialized too.
This means we can write tests properly without having to worry
about IdeApp.IsInitialized.

This allows us to create Gtk# projects in our test runner... hurrah!
Merge remote-tracking branch 'origin/master' into monodevelop-4.3.2-branch