Server-side persisted averaging for common intervals

[icasdri]

There's a limitation in instantaneous computing power on the client-side when doing averaging over very large intervals (to e.g. view an entire year's worth of data at once).

We should have the server calculate (upon collection) and persist averages over common intervals (with standard deviations so we can show fancy graphs), e.g. hourly and daily averages.

[icasdri]

Development on this (with a move to more generalized and streamlined data storage logic) is on branch savg.