add render() helper to jinja for rendering cherrypy "handlers"

e.g. render a url directly in a template, something like symfony's
render tag/function. especially useful with partial page reload with
ajax and such.
rewrite queue/player to use render() helper
added memoize helper
memoize some queue_dao methods

to avoid them being called multiple times due to it using {{ render() }}
lazy=joined queue.track for faster queue/list load
don't load queue on ajaxify/xhr request
some jinja StrictUndefined fixes
optimize adding of tracks to queue