Expand the tag abbreviation system introduced in b0be8ae45 so that it
works in searches and when tagging posts, not just in autocomplete.
For example, you can tag a post with /evth and it will add the tag
eyebrows_visible_through_hair. You can search for /evth and it will
search for the tag eyebrows_visible_through_hair.
Some more examples:
* /ops is short for one-piece_swimsuit
* /hooe is short for hair_over_one_eye
* /saol is short for standing_on_one_leg
* /tlozbotw is short for the_legend_of_zelda:_breath_of_the_wild
If two tags have the same abbreviation, then the larger tag takes
precedence. For example, /be is short for blue_eyes, not brown_eyes,
because blue_eyes is the bigger tag.
If there is an existing shortcut alias that conflicts with the
abbreviation, then the alias take precedence. For example, /sh is short
for suzumiya_haruhi, not short_hair, because there's an old alias for
/sh -> suzumiya_haruhi.
2c1da660fd