Add tutorial for client configuration

Summary

There should be a specification and tutorial for configuring the clients (e.g. in docs/tutorials/client_configuration.md)

• Add documentation for all config options in pylinkahead.ini
• Copy and extend if necessary the tutorial from https://docs.indiscale.com//caosdb-pylib/configuration.html#authentication
• Add (or create follow-up issues) documentation for linkahead-client.json (maybe not before it's also supported by pylib)