If the DAG API supports asking a card for the set of ERF types it supports, use that capability, to handle cards that support multiple ERF types. This is to support channelised/fractional T1/E1. Don't set the snapshot length - some DAG cards support multiple capture streams, but the snapshot length is global, so it'd affect other captures. Update README.dag.
updated API if available.
the DAG support checkin. Update FILES and INSTALL.txt.