youtube: Port to the YouTube API version 3

Deprecated API:
 • GDataYouTubeQuery:format, gdata_youtube_query_get_format(),
   gdata_youtube_query_set_format()
 • GDataYouTubeQuery:has-location
 • GDataYouTubeQuery:language, gdata_youtube_query_get_language(),
   gdata_youtube_query_set_language()
 • GDataYouTubeQuery:sort-order, gdata_youtube_query_get_sort_order(),
   gdata_youtube_query_set_sort_order()
 • GDataYouTubeQuery:uploader, gdata_youtube_query_get_uploader(),
   gdata_youtube_query_set_uploader()
 • GDataYouTubeSortOrder
 • GDataYouTubeUploader
 • GDataYouTubeContent
 • GDataYouTubeFormat
 • GDataYouTubeVideo:video-id, gdata_youtube_video_get_video_id()
 • gdata_youtube_video_look_up_content()
   (use gdata_youtube_video_get_player_uri() instead)
 • GDATA_YOUTUBE_RATING_TYPE_SIMPLE
 • GDataYouTubeCredit, GDATA_YOUTUBE_CREDIT_ENTITY_PARTNER
 • GDataYouTubeVideo:credit, gdata_youtube_video_get_credit()
 • GDataYouTubeVideo:is-draft, gdata_youtube_video_is_draft(),
   gdata_youtube_video_set_is_draft()
 • GDATA_YOUTUBE_*_FEED except GDATA_YOUTUBE_MOST_POPULAR_FEED (all
   others have been deprecated online and will transparently return the
   most popular videos from the past 24 hours)

API changes:
 • GDataYouTubeQuery:restriction no longer accepts IP addresses
 • All GDataCommentable functionality on GDataYouTubeVideo is disabled
   at runtime until the v3 YouTube API for comments is finished online
 • Not all properties of a GDataYouTubeVideo may be retrieved when doing
   searches, retrieving related videos, or listing standard feeds — to
   guarantee getting all properties, use
   gdata_service_query_single_entry() for the video in question; common
   properties such as title, description, player URI and thumbnails
   will always be retrieved

Internally, the GDataYouTubeControl and GDataYouTubeGroup APIs have been
removed, but they were never visible publicly, so this is not an API
break.

Due to the transition from v2 to v3 of the YouTube API, your client’s
developer key may stop working. Refresh it here:
   https://developers.google.com/youtube/registering_an_application

https://bugzilla.gnome.org/show_bug.cgi?id=687597