Tag subscriptions should follow tag name change

[garnetdagger]

Title
Tag subscriptions should follow tag name change

Short, concise description of the idea
When you are subscribed to a tag, and the journal owner changes the tag name, you should be subscribed to the new tag.

Full description of the idea
When you're subscribed to new entries with a certain tag in a certain journal, if the owner changes the name of that tag, you should be automatically subscribed to the new name of the tag.

(Currently, what happens is buggy, and gives you a broken subscription instead of a sensible error message; a support request to fix that bad behavior has already been filed, but since it doesn't give you a subscription to the new name, that would be a new feature.)
An ordered list of benefits

• Intuitive behavior.

An ordered list of problems/issues involved

• If the user makes everything in the tag not viewable by you and changes the tag name, this could break security.
• If the new tag has nothing to do with the old tag, this could be confusing.