Added support for extra fanart as backgrounds

- Added support for extra fanart as backgrounds in Movies and TVshows
respectively
- Disabled video info preview extra fanart (bug showing wrong image when
item does not have extrafanart)
- Set fadetimes to 600 (use to be 500)
- Disabled global background image(s) if fanart image exists in
libraries (trying to eliminate ghost image between fanarts)
- Added skin setting under Settings > Skin > Backgrounds to set
backgrounds time per image
- Rearranged skin settings, place 'Backgrounds' after 'Home'