* Reset default note range to 0..127 for step-entry and other users
* Allow to print label "C-<n>" on keyboard
* Fix 6 octave note range
* Save/load user settings in virtual-keyboard window
* fix key-range off-by-one 0..127
* allow to shift octave
* allow to configure note range
* highlight grand-piano range and keyboard-shortcut range
* proper piano layout (black key offsets)
* add support for DVORAK keyboard layout
(still incomplete: settings are not yet saved/restored,
_piano_key_velocity should become a HSliderController, ...)
* allow gtk_pianokeyboard to respond to y-axis click position
and include MIDI velocity with note-on signal
* add configuration settings to virual-keyboard
min/max velocity, keyboard-layout
* add a CC7 controller knob