Adding javascript requirements for #5695

js files need to be included with fpr-admin module, not be parent django app.
adding required css files.
allow FPCommand.output_format to be nullable.

Some FPCommands (like verification commands) do not have an output format.
filtering list of available commands when creating an fp rule.
Merge branch 'master' of git.artefactual.com:archivematica-fpr-admin
Merge branch 'dev/issue-5695'