Screen off: stop polling for now playing info.

If the user wants "Now playing" info to appear in their notification
area, make sure we don't poll XBMC every second while the screen is off,
as any new information cannot be seen until the screen is turned back on
anyway.
Added sort to getArtists() to sort results by name
Merge pull request #79 from tombriden/music_sort

The Artists list does not get sorted
Call updateProgress of now playing screen even when paused so the seek bar times still display
New boolean parameter in updateProgress to determine whether to display play or paused icon
commented out actor tabs from movies/tv while the api functions to get them don't exist
Merge pull request #60 from tombriden/now_playing_pause

Pressing play after pausing it in now playing restarts video
Merge pull request #59 from tombriden/remove_actor_tabs

No movie actors in Movie -> Actors
Fixed getting movie runtime
removed unused imports
Merge pull request #58 from tombriden/runtime

Runtime of movies displayed in seconds
Merge pull request #38 from otaconix/master

Don't poll XBMC for "Now playing" info if screen is off.
Fix import
ported code from hjhamala to stop now playing poller when no subscribers
Merge pull request #80 from tombriden/notification_poller

Notification poller
fix movie search
update to freezy master