Added Board Tags for Filtering, Meta and SEO.

Bitterli

OwnerAdminMod

@bitterli

Still working on filling in values for each board.

Comma separated input in settings. It's the easiest way and I want it just done.

Originally working on an overhaul to the site's meta information and SEO to give it slightly more visibility. I wanted each board to have its own tailored keywords in the metadata. Each board now has tags/keywords, each thread also gets these tags/keywords in its metadata.

Added in the filter thing for the boards list page. If the tag appears more than once, a dedicated link is there to only show those boards. Swap links to make it faster.

Added the full list of tags for each board in the boards list page. Also added it on the board specific page.