First pass at Gstreamer 1.0 porting.

This at least compiles against gstreamer 1.2.
Things that work:
* Playing audio
* Automatically completing tags

Things that don't work
* Spotify
* Moodbar

Things I haven't tested
* Transcoding
Merge branch 'master' into gstreamer-1.2
Merge branch 'master' into gstreamer-1.2

Conflicts:
	ext/clementine-spotifyblob/mediapipeline.cpp
	gst/moodbar/gstfftwspectrum.c
	src/core/songloader.cpp
	src/core/songloader.h
	src/engines/gstengine.cpp
	src/engines/gstenginepipeline.cpp
	src/moodbar/moodbarpipeline.cpp
	src/musicbrainz/chromaprinter.cpp
	src/transcoder/transcoder.cpp
	src/ui/mainwindow.cpp
	src/visualisations/projectmvisualisation.cpp
Allow to change rating when "inline" editing is not enabled
Pause spotify track (issue 2503)
(patch slightly modified, not sure why it wasn't applied before: it looks good to me)
Automatic merge of translations from Transifex (https://www.transifex.com/projects/p/clementine/resource/clementineplayer)
Better check (avoid to add invalid results, leading to a crash when adding this invalid item).
Fixes issue 3132, but I would like to improve this in a second step: clicking the provider adding all the songs for this provider to the playlist.
When clicking on a provider, on the global search result list, add all results from this provider to the playlist.
Fixes issue 3132.
Add seek ability to Spotify tracks.
This is functional but pretty hacky.
And, as noted in the comments, there is a small delay (depends, but usually several seconds) to have the seek taken into account. But IMHO it's better than nothing.
Fixes #2503
Remove dead code
Remove few Ubuntu One things remaining
Automatic merge of translations from Transifex (https://www.transifex.com/projects/p/clementine/resource/clementineplayer)
Added a preference to disable the pause notification. Fixes #2450.
Rewrite moodbar stuff for gstreamer-1.0:
- Rewrite gstspectrum (1.0) to use FFTW (2x faster) and emit raw magnitude
  values (not log scaled).
- Rewrite the moodbar generation code to be somewhat understandable, and
  do it in Clementine instead of gstreamer.
Various bits for gstreamer-1.0 compatability
Don't crash if we can't write to the moodbar cache
Merge branch 'master' into gstreamer-1.2

Conflicts:
	src/moodbar/moodbarloader.cpp
Make Spotify work with gstreamer-1.0.
Fix misleading offset_bytes names
Remove useless check