This is a preparatory commit for using isort for sorting all of our
imports, merging changes to files where we can easily review the
changes as something we're happy with.
These are also files with relatively little active development, which
means we don't expect much merge conflict risk from these changes.
This restyles and rewords some of the emoji style section to look
better and fit it more with the current style guide.
Tweaked by tabbott to modify the historical migration rather than
adding a new one. This is OK because the emojiset choices text change
doesn't touch the database; it's just a Django Python code thing.
Also removed translation tags, since we don't need them for a set of
brand names.