tracker-extract: Remove obsolete totem-video-indexer extractor

totem-video-indexer was removed in GNOME 3.2.

https://bugzilla.gnome.org/show_bug.cgi?id=726639
tracker-extract: Remove obsolete GStreamer fallbacks

Remove the tagbin and decodebin2 GStreamer fallback backends,
GstDiscoverer is easier to use, and less prone to problems.

https://bugzilla.gnome.org/show_bug.cgi?id=726639
tracker-extract: Add Gibest hash calculation to GStreamer

Add Gibest extract to GStreamer extractor, as used in the
OpenSubtitles service:
http://trac.opensubtitles.org/projects/opensubtitles/wiki/HashSourceCodes

extract_gibest_hash() written by Carlos Garnacho <carlosg@gnome.org>

https://bugzilla.gnome.org/show_bug.cgi?id=726640
tracker-extract: Remove obsolete xine extractor

https://bugzilla.gnome.org/show_bug.cgi?id=726639