Cache formLists

[gmaclennan]

Cloudflare is a very easy and cheap way to reduce server load, caching pages in a CDN. We can't use it on the route domain though because the timeout is too short for form submissions from a slow connection.
Currently creating the form lists is expensive (it calculates the md5 of each file every time), so this would benefit from being in a CDN. We could redirect formList requests to a subdomain that is cached on Cloudflare's network.
Worth the effort? Current in-memory caching in f3a3173 may be enough.
Another option to improve caching would be to cache components of a form list.