Add Configurable filter descriptions to torque

What it says on the tin, based on conversation in zulip here: https://chat.opentechstrategies.com/#narrow/stream/45-Lever-for-Change/topic/Explore/near/178214 . It could probably use another commit for styling. It allows html in the config, so a good test in your local settings might be:

$wgTorqueFilterDescriptions = [
  "competition_name" => "This is a <a href='https://google.com'>VERY IMPORTANT</a> help text.  It brings together the past, the future, and the present in a giant explosion of helpful words.  They include:<ul><li>help<li>text<li>brings</ul>",
];