Added more modules - wavetable and counter

I added the beginnings of a wavetable oscillator module and a very
simple counter module.  Both need some work.  More importantly, I
noticed that the constant module is broken because there's currently no
way for a module's output to avoid getting modified another module's
input.  Right now a module often bit-shifts its input into the range it
needs.  I'll be fixing that bug asap.