update all synths:

* move to using time (rather than Hz) as unit for modulating stuff. Use new param name
  phase (short for phase duration) to unify this
* move from ASR to ADSR envelopes on all synths. Default behaviour
  should be unchanged unless the following new params are specifically used:
  - decay
  - attack_level
  - sustain_level
* add missing info in rb metadata file
* beef up bells a little with more thickness
* add triangle wave form to tb303 synth (available with waveform 2)