lots of changes

* source is now available under GNU GPLv3 licence
* removed MIDI clock receive support, might add it later when I fix it
* rewritten analogue debouncing algorithm
* rewritten start-up routine
* rewritten button debouncing algorithm
* simplified debouncing of buttons (removed setDebounceTime function,
use setNumberOfColumnPasses instead)
* removed dirtyHack function, it's no longer neccessary
* general clean-ups and modularization of code
* bumped release version and dates in source files