vpr_autoid_read should function without measurement data

[EOGrady21]

vpr_autoid_read() currently requires both aid and aidmeas files to be input. Our new processing workflow will only create aid files. This function needs to be updated to skip over the aidmeas processing if meas files are not supplied.

This should be simple enough to contain the meas processing section in a conditional statement ie if missing(file_list_aidmeas){...}

[EOGrady21]

I have fixed this on my local branch but am getting some GitHub errors ('remote hung up unexpectedly') when trying to Push. I will try again later.