fix state exit functionality not being run in inventory

right click to exit inventory circumvented the functionality hooked to the
OK button
Clean up Battlescape popups.
Don't let user get stuck in the Scanner, that's just a horrible fate.
Revert "fixing" the scanner in favor of upstream changes
Merge remote-tracking branch 'upstream/master' into experimental

Conflicts:
	src/Battlescape/UnitInfoState.cpp
Handle onMouseClick instead of onMousePress in save/load screens (because touchscreens)