Tag Settings Menu Autosave

closes #4517

- adds autosave to name/slug/description fields in TSM
- adds nprogress indicator when saving
Yeah, it might not be a bad idea.

Slugs will get trimmed on the backend (`core/server/models/base.js#generateSlug`) but it probably doesn't hurt to also trim them here.

There isn't really a problem with descriptions containing extra whitespace but just for the sake of keeping things clean it's also probably fine to just trim them here as well.