Controllers Naming: Prevent duplicate names

For this, iterate through all given names and use the next name that's available.
ComboBox: added sizeHint() + coding style
TempoSyncKnob, Knob: allow construction without parent
InstrumentFunctionViews: manage widgets using layouts
added a demo song and reorganized LICENSES.TXT alphabetically
Renamed instrument function classes and instances

Arpeggiator got InstrumentFunctionArpeggio and ChordCreator got
InstrumentFunctionNoteStacking. All related views and instances have
been renamed for better consistency.
Merge pull request #137 from Lukas-W/stable-0.4-iss130

Issue #130: Controllers Naming: Prevent duplicate names
Merge pull request #138 from grejppi/stable-0.4-rdudr

another new demo song
Updating Authors file with new contributors
Merge pull request #140 from eagles051387/stable-0.4

Updating Authors file with new contributors