Refactoring Tasks

Here is where rryan keeps track of (typically small) refactoring tasks. This is doomed to become out-dated but oh well. As of 5/2013, this is up to date.

• Move keyboard processing into controller subsystem.
• Timestamp all MIDI/HID messages
• SoundSource API -> floats (breaks plugin ABI)
• SearchQueryParser -- SQL vs. internal
• #define all preference config keys
• Header file includes cleanup
• Make menubar nicer, get it and all action handlers out of MixxxApp
• If mix output is not used, don't calculate it in EngineMaster.
• move scanning-related code out of TrackCollection
• EngineObject API const-ness
• Preferences dialogs need a huge overhaul.
• Preferences depend trivially on PlayerManager. Also DlgPrefControls doesn't work with changeable #s of decks or preview decks.
• PlayerManager bindToLibrary is not changing-n-deck capable.
• SoundManager multiple sound cards FIFO buffer for outputs instead of mutex
• Engine deal with floats -1/1. get rid conversion on output in interleaving (would potentially speed up interleaving)
• vinyl control gain into vinyl control processor
• DISALLOW_COPY_AND_ASSIGN is redundant for QObject derivatives.