(CE-669) Add some client-side caching of anon SWM requests

Add 15 minute client-side caching of anon SWM checks and make use of
the last dismissed message ID to bust the cache when a message is
dismissed by the user.
(CE-669) Change Varnish and Browser TTL
Format with JS-Beautify
(CE-669) Move handling of dismissed messages to client

Moving the creation of the message HTML and removing the dismissed
messages to the client so that there aren't issues now that it will
be cached by Varnish and so the cached result is shared by all anons.
Add blank template to avoid fatals until anon cache clears
Merge pull request #2965 from Wikia/release-212-CE-669

(CE-669) Putting anon SWM checks behind varnish