Add support for using any of the current related tag types

Regardless of category or query. This meant that the category value
had to be passed in as either null or the value itself for both types
of functions. It also fixes an issue where the category wasn't settable
on the pattern matching type.

app/controllers/related_tags_controller.rb

@@ -4,9 +4,10 @@ class RelatedTagsController < ApplicationController
   def show
     query = params[:query] || search_params[:query]
     category = params[:category] || search_params[:category]
+    type = params[:type] || search_params[:type]
     limit = params[:limit]
 
-    @query = RelatedTagQuery.new(query: query, category: category, user: CurrentUser.user, limit: limit)
+    @query = RelatedTagQuery.new(query: query, category: category, type: type, user: CurrentUser.user, limit: limit)
     respond_with(@query)
   end
 end