Since #3334 didn't change much on d.m.org, this is another attempt to
speed up startup.
Given moderation bots like Mjolnir/Draupnir are in many rooms with quite
often the same or similar ACLs, caching the compiled regexes _should_
reduce the startup time.
Using a pointer to the `*regexp.Regex` ensures we only store _one_
instance of a regex in memory, instead of potentially storing it hundred
of times. This should reduce memory consumption on servers with many
rooms with ACLs drastically. (5.1MB vs 1.7MB with this change on my
server with 8 ACL'd rooms [3 using the same ACLs])
[skip ci]
* Move currentstateserver API to roomserver
Stub out DB functions for now, nothing uses the roomserver version yet.
* Allow it to startup
* Implement some current-state-server storage interface functions
* Add missing package
