Caching

This adds caching for the locale JS assets and improves the diagnostic output when asset retrieval/caching goes awry.
Only other thought is that maybe we should say we're modifying this file before writing it into the cache?

It's just that the order of the output seems odd (I think this existed before though) because after we grab the SERP Template (page_spice) we start grabbing the other assets before writing it into the cache (the last line shows page_spice being written but thats after 5 other files get written to the cache)

I suppose we could put it into the cache, then modify the cached file?