Index Gloss Tags

Functionality in the "Manage Glosses" page to index Gloss tags and store them in RERUM. This will provide helpful functionality for [an issue](https://github.com/CenterForDigitalHumanities/Gallery-of-Glosses/issues/59) for the [Gallery of Glosses public site](https://github.com/CenterForDigitalHumanities/Gallery-of-Glosses).

My proposal for the interface of this functionality is that the "more" button of the Gloss management modal (currently non-functional) will display another modal, where an authenticated user can choose to approve the list of tags for the list of tags, or to remove them from the list (if they are in the list already).