feature: Add environment variables for configuration

[sweco-semkni]

Resolves #195

Make it possible to set configuration values with environment variables, as an addition to the configuration values in the config files: dbconfig.js and config.js.

Configuring values in the configuration with environment variables, is useful when running the server in a Kubernetes server environment.

[MattiasSp]

Fixes #195, no? Add a note in the PR description to link the issue :)

[MattiasSp]

It looks like you have excluded all array config options, which makes many of the services still be dependent on the config.js and dbconfig.js files.

Would it be possible to add a simple-ish JSON deserializer to the config utility so that at least some smaller arrays could be entered as strings in environment variables as well?

Also, note that this PR currently does not support changing the database type from e g PostgreSQL (pg) to MS SQL Server (mssql) using environment variables.

I'll try to find time to test it soon-ish :)