* split main loop in two separate threads, using ProtoThreads 1.4 (see
http://arduinocollective.com/2009/12/05/arduino-threading/ and
http://www.sics.se/~adam/pt/)
* implemented simple key repeat delay: first delay is 1 second, after that it is
only 200 ms
* changed indenting (since multithreading was such a big change in it self, it
was relatively painless to do it now)