[WIP] #128 - Proof of concept for search kit task

This is messier than it really is, partly since the existing form does not have the literal word Form in the class name, which is fine when coming from a regular contribution search, but trips up CRM_Core_Invoke when coming from searchkit to a separate url.

And as-written it breaks the existing contribution search action.

But this is proof of concept that it can at least get this far.