Introduce Speed instead of Pitch/Rate, to match other place in Mixxx and Manual
https://bugs.launchpad.net/mixxx/+bug/1283190
User Speed term for combined Pitch/Tempo control in ControlPickerMenu
Fix some var names and comments to Speed = Pitch / Tempo
removed unused getPitchIndpTimeStretch()
Playback Speed without Slider
Increase/Decrease Speed
replace pitch-bend with Temporary Increase/Decrease Speed
Add number-of methods to PlayerManagerInterface.
AutoDJ fixes.

* Remove QSignalMapper usage and instead proxy signals from
  DeckAttributes.
* Connect track load / unload / failed-to-load signals from
  BaseTrackPlayer. Lays the groundwork for solving Bug #1396931.
* Add a helpful debug flag for tracing AutoDJ calls.
* Remove PlayerInfo usage from AutoDJ for getting the loaded
  track. Instead, use BaseTrackPlayer itself.
Make DeckAttributes fields private.
Make the tests reflect how real players react to track load requests.
Remove unused variable.
Address review comments.
Merge pull request #410 from rryan/autodj

AutoDJ fixes.
LateNight: Make sure coverart setting is persisted
Add a BindProperty transformation for boolean Not
explicit cast to bool
Deere: Use new <Not> transformer
Merge pull request #413 from ywwg/not-transformer

Add a BindProperty transformation for boolean Not
Skip unloadable tracks in the AutoDJ queue. Fixes Bug #1396931.

* On track load failed remove the failed track from the queue and load
  the next track from the queue to the deck.
* Update existing on-enable test cases to check what happens after
  receiving track load success signals.
* Add test case for ADJ_ENABLE_P1LOADED state failing to load the
  first track.
* Add test case for ADJ_ENABLE_P1LOADED state failing to load the
  second track after successfully loading the first track.
* Add test cases for single-deck-playing AutoDJ enable failing to load a
  track in the non-playing player.
* Add test cases for P1FADING / P2FADING mode successfully loading a
  track and failing to load a track.