Investigate possibility of logging to PostgreSQL

[spbnick]

PostgreSQL has recently added support for JSON storage and indexing.
@plaes asked if something like this could be used for the backend.

Investigate what's possible with this solution and what it could take, roughly, to use it.

See https://fosdem.org/2017/schedule/event/postgresql_infrastructure_monitoring/
and http://www.slideshare.net/StevenSimpson30/infrastructure-monitoring-with-postgres

[spbnick]

If anybody is going to be using a system like this, then it is likely that there will be a place for ingesting tlog/aushape JSON as is in the stack, and no additional code will need to be done on our part. The data will be stored as JSONB and would allow sorting and queries for data sufficient for playback purposes, with retrieval of original JSON, I assume. Technically there doesn't seem to be any major hurdles to implementing this. However, separate retrieval and querying back-ends will have to be used compared to Elasticsearch.