- CVWidget: properly detect new MIDI-devices and add them to AbstractCVWidgetEditor.midiSources
- CVWidgetMSEditor: set the midiMode-popUp according to midiMode in each slot of the multi-slider - if they vary set the display to "--"

Signed-off-by: nuss <st9fan@gmail.com>
cleaning up various methods in CVWidget (setting up functionality according to the class passed in)
getting display of midi-options in CVWidgetMSEditor and CVWidgetEditors within CVWidgetMS right (not finished)

Signed-off-by: nuss <st9fan@gmail.com>