Do not show Wikidata items in the tag autocomplete dropdowns

[samwilson]

At the moment, there's an annoying two-stage loading of the autocomplete dropdowns for tag entry. First it loads any matching local tags, and then after a moment it appends any matching Wikidata items it finds. This is annoying, because it jumps around and changes what's available while you're trying to select it, and it also is slower than it should be (because of the extra requests to the Wikidata API).

I think the Wikidata items should be left out of the autocomplete list, and only used on the tag edit form when associating a tag with a Wikidata item.

[samwilson]

Done.