queue search UI

> I could use help with the skins because I'm not very skilled in that area.
> All skins were made by volunteers and I'm struggling with the maintenance.
> Especially the craftier Javascript parts.
> 
> As an example: I've been trying to add a search box to the queue in Plush,
> like the History has. I haven't succeeded...

Searchable queue will require some updates to the python API (hopefully easy for you), but the UI work is now done in this pull request (easy for me).

Changes tested in Chrome, Firefox, and Safari.