db.clj refactoring

[jsmassa]

[jsmassa]

Closes #525

[kordano]

Could you check if that works with the latest rebase as well?

[whilo]

This looks good to me as well, but it is a bit difficult to see whether the functionality has changed somewhere or whether functions have just been pulled out to different namespaces. I think it is the latter and in this case everything should be fine.

It is a bit annoying that I have to rebase my two open PRs for the GraalVM support and the global address space again after this, but hopefully it won't cost me more than a few hours. Ideally we should settle PRs affecting functionality before doing refactorings like this and plan this a bit ahead to avoid such rebases.