artists: make artist pages less shit.

* Group URLs by site.
* List most important URLs first and dead URLs last.
* Add site icons next to URLs.
* Put other names and group name beneath the artist name, instead of beneath the wiki.

app/models/artist.rb

@@ -34,7 +34,9 @@ class Artist < ApplicationRecord
     extend ActiveSupport::Concern
 
     def sorted_urls
-      urls.sort {|a, b| a.priority <=> b.priority}
+      urls.sort_by do |url|
+        [url.is_active? ? 0 : 1, url.priority, url.domain, url.secondary_url? ? 1 : 0, url.url]
+      end
     end
 
     def url_array