Dakimakura stuff

Brought up on Discord to...

rename dakimakura -> dakimakura_(medium)

EDIT: See below.

BUR #4058 has been approved by @evazion.

create alias dakimakura -> dakimakura_(medium)

Just a "simple little" step of disambiguating it.

EDIT: The bulk update request #4058 (forum #176629) has been approved by @evazion.

Makes sense. As mentioned on Discord, we do this for terms like photo and poster which have both medium and object tags, and there's examples of users understandably mistaking the dakimakura tag for dakimakura (object).

I'm changing this to an alias because even though the tag is somewhat ambiguous, it's also a large and well-known tag. We can live with an ambiguous alias for a little while longer. The alias can be removed at a later date after everyone is onboard with the new tag.

The bulk update request #4058 (forum #176629) has been approved by @evazion.