more flexible metadata edits

[kzuberi]

We've have an optional config file to be able to record simple metadata edits, for things like changing an individual files network group classification or default selected flag. But it seems like we also need to be able to do this for sets of files, like all those with a certain network group code, since the import system doesn't set the defaults as needed.

May be able to add this by making the batch_edit_metadata.py script more flexible, take a key and value wildcard for selection, and a key and value for setting. Unfortunately this seems a bit complex to explain and keep track of, so probably the batch edit file needs to be more user friendly, allowing comments and more descriptive specification of the rules.