Revert "Build a libmixxx.a and link it into mixxx and mixxx-test."

This reverts commit 63464477257b698ae475cfbff40a74428a8279ec.

Conflicts:
	src/SConscript
Merge pull request #148 from ywwg/vinyl-abs-fix-2

Updates and fixes to vinyl control
Add getKey() method to ControlObjectSlave.
Since WBaseWidget is common to all skin widgets now, simplify the MixxxApp tooltip event handler.
Use WLabel for the "No OpenGL detected" fallback message.
Add emitOptionToString helper.
Add toDebugString() method to ControlWidgetConnection.
Show debug tooltips when developer mode is enabled.

Provides useful information for skin writers in widget tooltips when in debug
mode.
Add connection control parameter to connection debug string.
Eliminate misleading precision in the bpm and rate displays.
* Show only one decimal place for bpm and rate
* Waveform stretch reacts more slowly to small changes in rate.
* Vinyl control bpm updates are much more sticky.
Reduce redundant subtraction
Have WNumbers the NumberOfDigits parameter and set a default of 1 decimal.