[gui] adds listitem info label inprogress to determine if epg item is in progress

This adds a new listitem info label inprogress which indicates if the
associated epg tag points to a current ongoing program.
Added Container.IsUpdating
jsonrpc: expose specialsortseason and specialsortepisode for episodes
[builtins] PlayMedia() should use a sort order appropriate for the items. fixes #15136
upnp: fix sort by upnp:rating
upnp: ignore "Unknown" as a single genre as it is added by Platinum
CDateTime: extend SetFromW3CDate() and add GetAsW3CDate(), GetAsW3CDateTime() and SetFromW3CDateTime()
upnp: fix serialization/deserialization of datetime properties
move ISliderCallback into its own header file
guilib: don't abuse and redeclare SPIN_CONTROL_TYPE_FOO
CGUISliderControl: fix SetIntValue() and SetFloatValue()
upnp: add some potentially useful logging to CUPnPPlayer::PlayFile()
Merge pull request #4614 from Montellese/upnp_player_logging

upnp: add some potentially useful logging to CUPnPPlayer::PlayFile()
Merge pull request #4608 from Montellese/gui_slider_cleanup

CGUISliderControl: some cleanup and fixes
Merge pull request #4606 from Montellese/upnp_fixes

upnp: some fixes
Merge pull request #4596 from Montellese/jsonrpc_properties

jsonrpc: expose specialsortseason and specialsortepisode for episodes
fix resume behavior for plugins with stack  

Resume behavior for local files (.-partN) are not corrupted.
http://forum.xbmc.org/showthread.php?tid=192690
Merge pull request #4616 from kit500/master

fix resume behavior for plugins with stack
Merge pull request #4601 from jmarshallnz/play_media_sort_order

[builtins] PlayMedia() should use a sort order appropriate for the items
[gui] fix incorrect parsing of relative <width> and <height> tags