Tags central management

Implement central tag management:

• Be able to create new tags in the central tag list
• Be able to edit tags in the central tag list (e.g. to fix typos), and make those same edits automatically on any records where the tag is used
• Be able to reassign all instances of one tag to another tag, and the delete the (now unused) tag from the central tag list and any records it was used on
• Be able to delete a tag from the central tag list and remove the tag from any records it is assigned to
  This would be phase 2 of tags development, following phase 1 ASAP

Functionality is similar to what charlotte needs in UIIN-162 when editing and/or deleting an optional format term defined locally in Inventory. If a tag is changed, change on all associated records. If a tag is deleted, throw a warning before deletion, and then delete from all associated records.