dvdplayer: ff/rw/seek was broken for inputs implementing IDisplayTime

This affected PVR with file based inputs and BluRay.
CGUIMediaWindow: fix invalid filter-path when toggling watched mode which leads to not grouping into movie sets
dvdplayer: another fix for seeking/fw/rw in PVR
[pvr] fix channel import for mysql backends. closes #13810
fixed - don't try to go to the previous window when stopping playback on exit. closes #13884
[pvr] fixed canceling the active timer on a channel in certain situations
moved nyxboard power and user button from peripheral config to keyboard.xml
reset initial visible state to visible if it has been set to delayed during a previous window session. fixes #13923
revert part of 60b0ee01a47a134a002594ab746b2e52efb0d2b7 that somehow snuck in
view control in login window was cleared on deinit rather than on unload. fixes #13813.
album art for individual songs in file mode weren't loading correctly - fixes #13906
always add the repository to the add-ons database even if it returns no add-ons. fixes constant (every 10 minutes) hitting of add-on repos that have no add-ons
Correct handling of multimedia key presses
[cec] don't send incorrect pause/resume to slideshow when the source is (de)activated and don't resume playback when the source is activated and we didn't pause it when the source was deactivated
[cec] don't update the device type in settings with the value that was returned from libCEC