uploads: allow changing thumbnail size on My Uploads / All Uploads pages.

* Add a "Size" menu to the My Uploads / All Uploads pages to allow
  changing the thumbnail size.
* Make the My Uploads / All Uploads pages use the same thumbnail size as
  the post index page.
* Change the "Gallery | Table" links on the My Uploads page to icons.

app/helpers/application_helper.rb

@@ -62,6 +62,10 @@ module ApplicationHelper
     html.join(" | ").html_safe
   end
 
+  def current_page_path(**params)
+    url_for(request.query_parameters.merge(params))
+  end
+
   def nav_link_to(text, url, **options)
     klass = options.delete(:class)