v0.0.13: Implement lock-free DB transactions.

Lock-free write transactions allows GraphKB to have multiple instances
running in parallel to scale out.

To implement the feature I added the source breakdown in 'assets' and
'relations' tables. That way there is no concurrent access to pivot
points anymore since each data source produces and manage its own entry
in the DB. The reconciliation is done at query time once the entries are
retrieved from DB.

v0.0.12

Add metrics exporter for prometheus to scrape.

v0.0.11

Build go-graphkb on debian instead of alpine.

v0.0.10: Build go-graphkb in docker.

This avoid adherence with the CI service.

v0.0.8

Add option to allow using cleartextPassword in DB SDN.

v0.0.7

Add more information in errors raised for debugging.

v0.0.6

Add query historizer to troubleshoot when a query takes too long.

v0.0.5

Fix bug with column name.

v0.0.4

Fix some misleading logs.

v0.0.3

Combine two messages in one when starting server.