Optimize Find

In ahau/ahau#34 there's a task "ssb-profile, optimize the Find by using ssb-search2 (need to modify ssb-search2 for that)"

I started modifying ssb-search2 https://github.com/ssbc/ssb-search2/pull/5 but realized that's probably out of scope for that module and fitting that feature into there would be pretty clumsy.

I wonder if this MR might be optimization enough. Otherwise we would have to make some custom db plugin I guess but I'm not sure how to do that.