Have Actor/ICC load from pfs_instdata YAML file instead of per-actor ConfigParser file

The connection to the tron hub and the actor logging are configured from per-actor files – e.g. "xcu_n3.cfg". Those declarations are nearly all identical and are not interesting. All interesting per-actor configuration (alarm levels, detector voltages, motor ranges, etc) have been pulled out from those files into $PFS_INSTDATA YAML files.

Move the remaining few configuration knobs to a $PFS_INSTDATA YAML file and arrange for the Actor and ICC classes to load those.