logging could use some centralization

[mfb]

The pushserver is logging in a few different places: /home/pushserver/logs/pushserver/push_server - mostly messages about deleted subscriptions /home/pushserver/logs/supervisor/pushserver_stdout - mostly db logs for subscription INSERTs and SELECTs

It would be nice to push errors and exceptions to Sentry (and centralize the info-level logs in one file on the app server if possible)