Add logging for PalmSystem methods

Signed-off-by: Simon Busch <morphis@gravedo.de>
Add support to focus/unfocs application window from app side

This is needed to maintain compatibility with old core webOS applications which acts with
a non visible window as manager component and keep the user visible window hidden until
the app is relaunched instead of closing it.

Signed-off-by: Simon Busch <morphis@gravedo.de>