#i123862# use O*String's isEmpty() method to check for emptiness in chart2 module

Patch-by: j.nitschke@ok.de
Review-by: hdu@apache.org
#i124201# rename apple_remote's MainController to AppleRemoteController

having a MainController class in the global namespace of an application with
gazillions of MVC patterns is not a good idea. Renaming it to better match
its scope (i.e. the Apple Remote) cleans this up.