Integration of songs in GuidoView
Refactoring
Created minimal project to find the GuidoView bug
More beautiful scores
Integrated PlaybackHandler
Finished SignalManager
Comment out statement inducing "Process error"
Fixed Bug
Revert "Fixed Bug"

This reverts commit fc74d2614eb4716fa396e5aa6c9a3e9d0d5ea246.
Bugfix: signals from playbackhandler and signalmanager come from
different threads. So make connection Qt::QueuedConnection
Bug still remains but disappear after resizing...
Merge branch 'guidoviewstuff'