Local JSON Import

[tw2113]

Despite what I said in: https://github.com/WebDevStudios/custom-post-type-ui/issues/381#issuecomment-266074940

I think there's room to work here and whatnot.

We would definitely want to exit early if there's no local spot involved, so that we're not doing a ton of reading. Also I know that people keep pointing out ACF, which has import into their view, which is a hidden post type, while we just have our couple of options.

Do we know what caching may be going on in ACF, that we could leverage in a similar way, if there's any caching at all? Is there case just one of being limited to editor/option screens as opposed to init hook which loads every page load?