Add ability to delete versions of datastreams

[mjordan]

From discussion starting at https://groups.google.com/d/msg/islandora/q1udVKoh194/YJD_4ulqCAAJ.

[mjordan]

Thinking a command like this is suitable. In this case, it would delete version 0 (the current one) and 1 (the previous one): drush islandora_datastream_crud_delete_datastream_versions --user=admin --dsid=FOO --versions=0,1 --pid_file=/tmp/delete_foo_versions_from_these_objects.txt

This would require knowing which versions you want to delete. If use cases for knowing the created date on the version to delete come up, we can address them then.

[bondjimbond]

A case for this functionality has come up for me, as old versions of large derivative datastreams are cluttering up the repository. In my use case, I would like to delete all but the current version from a list of PIDs.

[mjordan]

@bondjimbond if you can test @patdunlavey's PR I'll merge it.

[mjordan]

Resolved with 4feafbf.