Improved back handling in mobile app.  Now more consistant with standard.
Just some code clean up.
* removed not used import
* handle home button correctly
* update currentPane after backStack.pop()
* removed JS backstack (not needed anymore)
* removed JSInterface exit method
removed forgotten setupBackButton function call
got back long press on portal functionality
bumped version number
* display backstack correctly on home button
* clear backstack on home button pressed
set currentPane to home if home button is pressed
added forgotten getString(...)