Add support for uploading posts from Gelbooru. Note that the translated
tags will include both the Gelbooru tags and the tags from the Gelbooru
post's source. The commentary and artist information will also be taken
from the Gelbooru post's source. The source of the Danbooru post however
will be left as the Gelbooru post itself, not as the Gelbooru post's source.
Don't show deprecated tags in the related tags or translated tags lists
when editing a post. It doesn't make sense to recommended adding tags
that can't be added to the post.
