Making a "merfolk" parent tag for Mermaids and Mermen

BUR #56081 has been approved by @nonamethanks.

create implication mermaid -> merfolk
create implication merman -> merfolk

I recently uploaded an image of a 1other character who is a mermaid (post #10972974) unfortunately because of the monster girl implication that means this image is now erroneously tagged, merman also has the equivalent implication for monster boy meaning there is no true gender neutral tag for 1other characters. You can see other examples of this in 1other mermaid solo where characters are being given monster_girl tags even though they are not 1girl (post #4365930 post #2916353)

One solution for this is to create an umbrella tag for all Mer characters, this would mean these 1others can just be tagged with the merfolk tag without needing to worry about a secondary monster_* implication.

Yeah we have a bunch of posts like post #10986496 that don't quite fit under either. The alternative is to make mer_creature or something for mermaid monsters - we do have unconventional mermaid, but it's a bunch of different concepts, and then again that would leave us with no way to search for merfolk in general.

This will need thorough cleanup.

The bulk update request #56081 (forum #423122) has been approved by @nonamethanks.

BUR #56371 has been approved by @nonamethanks.

create implication unconventional_mermaid -> merfolk
create implication kneeless_mermaid -> merfolk
create implication mermaid_with_mermaid -> merfolk
create implication mermaid_out_of_environment -> merfolk

These can now imply the base tag. Not sure if they should also be renamed.

BUR #56372 has been approved by @nonamethanks.

create alias unconventional_mermaid -> unconventional_merfolk
create alias kneeless_mermaid -> kneeless_merfolk
create alias mermaid_out_of_environment -> merfolk_out_of_environment
create alias mermaid_with_mermaid -> merfolk_with_merfolk

Not a big fan of these but it's better than their current name.

The bulk update request #56371 (forum #424073) has been approved by @nonamethanks.

The bulk update request #56372 (forum #424075) has been approved by @nonamethanks.