LPD memory cell constant parameter

Have added parameter, now to see about making it convenient to set it... Some options, in order of preferable to not preferable:

1. Condition watcher looks at control device and guesses (probably with devices themselves occasionally checking using one of the other methods)
   • Challenge: I can't seem to find FXE_DET_LPD1M-1/CCML/VETO or similar sources in saved runs, so not much to go by
2. Condition watcher subscribes (briefly) to output channel of some DAQ and glances the cell table
   • Challenge: middlelayer...
3. Correction devices update themselves based on input
   • Downside: manager doesn't know what's going on
   • Option: only check every N'th train
   • Option: add slot to only update once based on next valid input