Admin: delete statemachine's CADC polling method
DB: add support for the md5 column in output_files

The get_output_files and set_output_files methods now allow
this new column to be accessed.  By default get_output_files
retains its old behavior (and returns plain file names)
but set_output_files now needs to be given a list of file
information objects with filename and md5 attributes.
Action: read md5sums when finding job output