@orta => Fixes #286.

Kind of a weird fix, but I'm essentially taking advantage of how view controllers walk up, or don't walk up, their hierarchy when presenting view controllers. By wrapping the app view controller in a nav controller that is itself contained in another VC, I can present help on top of everything (the window's root VC) and present the modals on top of the views in the app VC (not not on top of the Help VC). 

Fixes #286.