Save only lens paper and standard source channels for which there are connected PMTs #78
Description
The lens paper can produce a fairly large quantity of data (especially if run at multiple gains). So we don't want to be saving data for channels that don't have connected PMTs. Figure out which PMTs are connected and enable only those channels.
Note: there may also be bugs associated with asking for channels 1:4 on rigs that have fewer defined PMTs. NeuroVision has only 3 PMTs but PMT1 is still present as a dummy...