Prodocols with 2 Multiclamp devices run slower than they should

[lcampagn]

This is because the multiclamp commander takes about 300ms to switch between channels (this is completely rediculous).
The best way around this is probably:
  - Only read/write MC commander settings at the beginning of a sequence, and hope they do not change during.
  - But for single-channel recordings, it is safe to read/write for every trace.
      (so we need some minimal communication between the channels.. perhaps a way to ask the driver whether a certain request will be very expensive?)