Specify frame types (ABCD) to allocate from OCS

For display, archiving, and "shepherding" purposes, it would be useful for the PFS side of ics_gen2Actor to specify which frames we request for a given PFS visit. For instance, only the 1st visit at a given field is likely to require MCS PFSC frames – we should not request them otherwise.

The proposed mechanism is to call SIMCAM.reqframes or ocs.getFrames, or a wrapper around them, with a set or dictionary specifying the details. TBD from negotiation with Eric.