perf(languages): improved js caching of languages by using simplecache

fixes #7458

This replaces the ajax language views which booted the engine every view to only report a 304 not modified... this fix replaces this with just a few milliseconds and a normal cacheable .js file if you use tools like Varnish
We should document that this is a trick to make the individual language views available for simplecache, and make them all just defer to the js/languages view. The problem this creates is that the js/languages view will result in many missing view notices.