initial step for playing from the harp note model
also highlights partially while playing
Now also the tune does a multiple selection
Now follow Q: directive while playing
Now can stop playing

updated abcjs to https://github.com/bwl21/abcjs/commit/7ecd2cdcc422392f6a8bf225a96327206b5b0ccf which is based on https://github.com/paulrosen/abcjs/commit/ef31061c8f6b6a1dca065b533ae44c9903f060e9

Still problems with too many selectionChanged events form the editor
suppress selection in editor while playing a song

improved parser messages
merged 'Bernhard' to 'develop'
refined layout on the screen
Merge branch 'song-player' into bernhard

* song-player:
  refined layout on the screen
Merge branch 'feature/song-player' into develop
Merge branch 'bernhard' into develop

* bernhard:
No longer show invisible rests
Optimize cropmark position
improved handling of tempo
removed superfluous line
fixed bug in rest handling
a bit ui improvement
Get an event when playing of song stops
refined rending process such that we can have activity indicators
Merge branch 'feature/activity_control' into develop
Merge branch 'develop'

* develop:
  refined rending process such that we can have activity indicators
  Get an event when playing of song stops
  a bit ui improvement
  fixed bug in rest handling
  removed superfluous line
  improved handling of tempo
  No longer show invisible rests Optimize cropmark position
  refined layout on the screen
  suppress selection in editor while playing a song
  Now also the tune does a multiple selection Now follow Q: directive while playing Now can stop playing
  initial step for playing from the harp note model also highlights partially while playing