Enable adding many tags at once to controlled vocabularies via API

[seanh]

We already have API calls for adding one tag or removing one tag at a time to/from a vocab. Want more convenient ways to add or remove many in one call, or just pass in a list of tags to completely replace a vocab's current list.

• Add tags_create() function that calls the existing tag_create() many times?
• Also tags_delete()?
• Or just let tag_create() and tag_delete() accept a list?
• Add tags argument to vocabulary_update() to pass in a list of tags to replace the vocab's current tags? (But it should still be possible to simply rename a vocab without changing its tags and without having to pass in the tag list.)