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
This file would need to document that this view shouldn't be used directly, but rather js/languages/LANG.js should be used and it *must* be view a simplecache URL or the language selection will fail.