Replaces the hardcoded list of emoji_names and unicode_emoji_names in
static/js/emoji.js with a list generated from emoji_map.json, both to get
the list out of version control and so we can start modifying it for our
autocomplete. This does not change the contents of emoji_names. It sorts and
removes duplicates from unicode_emoji_names (causes no change in behavior,
since unicode_emoji_names is only used as if it were a set).