query cache

[tantaman]

We should be caching query results and/or resolving queries as much as possible from the app-cache.

This'll keep all things instant post pre-fetch. This is really only a problem for the browser where non-trivial queries against sqlite backed by indexeddb can take ~5ms rather than microseconds.

~5ms doesn't seem so bad but if the user has 4 complex queries to resolve before updating the UI it'll be above our ideal threshold of 16ms.

[tantaman]

#46 is another related improvement by enabling parallel reads.

[tantaman]

In node / ios / android / desktop this is a non-issue as queries resolve in microseconds.