Support multiple associated datatypes

[tsalo]

Detailed Description

phys2bids currently only convert physio data associated with fMRI (i.e., data under the BIDS func datatype). It would be good to be able to output files in any of the BIDS datatypes that support associated physio data. Currently, I think that's just beh, but I believe that's more of an oversight in the specification than an explicit rule.

Context / Motivation

This will benefit users who want to convert physio data not associated with fMRI data.

Possible Implementation

Perhaps add a field to info in the heuristics file, corresponding to datatype.

[smoia]

Another possible implementation is to add a flag in the parser (-beh and others) to tell the program to change the destination folder.
Alternatively, we can use different -in flags to indicate the same concept. @tsalo do you know if we can create a parser that has a required [field OR another field]?

[tsalo]

argparse's add_mutually_exclusive_group() has a required argument, so you could specify that users must provide one of the arguments in the group, but no others.