import chromaprint feature from libray_features branch
removed option to submit keys
added copyright information
code clean up
adpot code to coding guidelines
removed bulky stuff that was not needed anymore
added API-KEY for mixxx
added KEY URL
merge with trunk
merge with trunk
removed musicbrainz url that is not used
merge with trunk
fixed signal connection
Merging from lp:mixxx.
Pull vinyl control input registration out of PlayerManager.
Refactor vinyl control processing to use a single thread and do no processing in the engine callback.

* Get rid of VC locks in the engine.
* Separate processing logic from VinylControlManager into VinylControlProcessor.
* Move vinyl control constants to a defs_vinylcontrol.h file.
* Write samples to VinylControlProcessor using a non-blocking FIFO.
* Write signal quality information to the signal quality widgets and
  WSpinny using a non-blocking FIFO on a 20ms update interval.
* Delete VinylControlProxy -- in the future should use inheritance
  rather than composition to implement multiple VC backends.
Fix off-by-one error in VCM.
Disable noisy log statement, eliminate redundant code.
Merging from lp:mixxx.
Get rid of read-write mutex since it is more deadlock prone than a recursive QMutex. Try to unlock the mutex when possible before triggering other logic to prevent deadlocks.