use same method for fs access for lookup albumart
cache album art lookup for directory
cache album art lookup for directory more
unregister jack broadcast receiver on destory
add start stop fsscan capability, stopping when exiting the app
file chooser should only react on db changes if visible, otherwise update on becoming visible
not really fix concurrency problem, but minimize it
Merge pull request #36 from Hoene84/master

Reviewed Fs scan