This is a first pass at building a framework for collecting various
stats about realms, users, streams, etc. Includes:
* New analytics tables for storing counts data
* Raw SQL queries for pulling data from zerver/models.py tables
* Aggregation functions for aggregating hourly stats into daily stats, and
aggregating user/stream level stats into realm level stats
* A management command for pulling the data
Note that counts.py was added to the linter exclude list due to errors
around %%s.
This automatically loads settings, zerver.models.* and
zerver.lib.actions.* when you start `manage.py shell`, which should
save a bit of time basically every time someone uses it.
Fixes#275.
Anders Kaseorg
rht
Aditya Bansal
umkay
Tim Abbott