Telephone state

[ppareit]

Add options: "Show system bar when ringing" and "Hide system bar when hang up".

[ppareit]

Two small problems with this at the moment.
(1) I currently don't have a android telephone that shows the systembar.
(2) This would need an extra permission (READ_TELEPHONE_STATE or something) and I prefer to keep number of requested permissions down to the absolute minimum.