Fix #5179: Add wiki page versions to wiki page secondary links plus standardization

* Call it "Changes" when referring to the global list of changes (pool changes, artist changes, etc).
* Call it "History" when referring to the history of a single item (pool history, artist history, etc).
* Put the artist history search form on the /artist_versions page, and remove the /artist_versions/search endpoint.

app/views/wiki_pages/_secondary_links.html.erb

@@ -4,6 +4,7 @@
   <% if policy(WikiPage).new? %>
     <%= subnav_link_to "New", new_wiki_page_path %>
   <% end %>
+  <%= subnav_link_to "Changes", wiki_page_versions_path %>
   <%= subnav_link_to "Help", wiki_page_path("help:wiki") %>
   <% if @wiki_page && @wiki_page.new_record? && @wiki_page.try(:tag).present? %>
     <li>|</li>