Another go at fixing fx trigger timing:

* Fx are now triggered at vt which means they can 
  now be used properly for rhythmical purposes
* To ensure FX chain order, groups are created at 
  RT in the appropriate order, and the vt triggered
  fx synth is placed into this new group
* We therefore now need to differentiate between
  the main FX group for the run and the 'current' 
  FX group when in a chain.