Horizontally scalable server with cockroachdb

[leon3s]

Following up this issue: #59
I think we should consedere drop postgresql to use cockroachdb.
Cockroachdb use the same postgresql driver so it should be as easy as changing the docker image used.
And it will allow better and easier scalability since all cockroachdb node can be write node

[ImBIOS]

@leon3s I think it'll better if you attach something like a performance benchmark or some proof of concept of the performance benefit.

[darioalessandro]

@leon3s so right now we do not even use a database XD.