Added wavetables

Added pretty much the same wavetables as I used in the previous
experiment. Added a test routine to the main program which outputs a
sine at 440hz (or so it should be) for about a second and keeps
statistics about the time that is left after every sample. Results are
shitty, the Pi seems to randomly lose up to 20 microseconds now and
then. In addition the side output has a stutter in it. Things are not
well.

Also I added a serial logger to the uploader script.