Fixed bugs related to JSON serialization
Fixed bugs related to JSON serialization

1. Fixed a bug which caused the octave attribute of Music to always be a
   string, thus causing parsing problems
2. Fixed a bug which caused edges to only being added to the edgeData
   map after the editing it, because vis.js only adds the default ID to
   an edge after the callback has been called.
   (See https://github.com/almende/vis/blob/master/lib/network/modules/ManipulationSystem.js#L1097-L1099)

sternenseemann/likely-music,sternenseemann/likely-music