Make cache / database mountable in docker-image

[JeroenKnoops]

Problem

We're currently using a h2 database and local cached versions of scanned dependencies.
This can not be mounted right now and therefore everytime you start your docker image, the database and the cache is empty.

Proposal

• Make h2 db mountable so you can choose to reuse the database.
• Make cache mountable so you can choose to reuse the cache.

[timovandeput]

The H2 database is currently hardcoded to be stored at jdbc:h2:file:~/licenses_db. I guess we can mount this database store from any persistent location on the docker host.

Note that the H2 database file cannot support multiple clients, and I have experienced an unrecoverable file corruption before.

(I am not sure what you mean by "the cache".)