Allows slime people to change color in lobby.

[tigercat2000]

This PR allows for slime people to select their color in the setup character menu.
The SQL schema has been updated to save this preference, which should be taken into account on downstream server databases.

[mvanalphen]

As all donators with the slime color changer fluff item have been contacted (and only one responded after more than a week), we're good to have this one in once the 24h period passes.

This includes a MySQL change. Do not merge/patch this until this change has been applied to the database.

[ZomgPonies]

Also make sure the slime colors update properly in proc/update_preview_icon

[tigercat2000]

Slime people previews do not work at all.- Note, working on this issue now, also working on getting ID cards to properly display color, as slimes can spawn with a chosen color, it should be on their ID's

[tigercat2000]

@ZomgPonies proc/update_preview_icon and datacore rendering of slime people color on PR #548 is working

[Spacemanspark]

Tajaran always appear black on their ID card, mind looking into that as well?

[tigercat2000]

That is beyond the scope of this PR, but, I'll look into it once this is merged/closed

[Spacemanspark]

Alrighty.