posts: use storage manager to build file urls.

config/danbooru_default_config.rb

@@ -257,13 +257,6 @@ module Danbooru
       # end
     end
 
-    def build_file_url(post)
-      "/data/#{post.file_path_prefix}/#{post.md5}.#{post.file_ext}"
-    end
-
-    def build_large_file_url(post)
-      "/data/sample/#{post.file_path_prefix}#{Danbooru.config.large_image_prefix}#{post.md5}.#{post.large_file_ext}"
-    end
 
 #TAG CONFIGURATION