[devel] Now Playing Widget changes

[Skin Settings]
- added Developer Mode
—> Widget Settings are now only visible when Developer Mode is turned
on because it needs a complete overhaul

[Home Screen]
- Player Fanart is now shown as background of Now Playing Menu on Home
Screen
- ability to enable TV Show ClearLogo/ClearArt/Poster from Widget
Settings; they show up when option „Display Playing Video in
Background“ is enabled