Create Post/Tag/Remove module class and route

- Fix tag name parameter in single tag removal link in mod/photos
- Remove "/post" from backend routes as it was preventing sessions from working in this module. No existing module had a route starting with "/post".

src/App/Mode.php

@@ -68,7 +68,6 @@ class Mode
 		'objects',
 		'outbox',
 		'poco',
-		'post',
 		'pubsub',
 		'pubsubhubbub',
 		'receive',