Implement full app lifecycle API

I'm told on #ubuntu-touch that the app should restore from it's non-active state exactly as it was before entering non-active state.

Currently, if I have started entering text for a task (either in the quick-entry box on top or via the bottom swipe feature) I will loose all of this if the app is put into non-active state before I save or add. Partially entered text should be included in the apps saved state and be restored to the user.