Gremlin-Python usability and tutorial

The Gremlin-Python environment is not useable "out of the box" at this time and hard to configure. It needs a specially configured gremlin-server for each use case.

The handling of the server configuration and startup could be simplified if it would be done by some kind of API instead of the YAML file. Especially it is important to make graph io available to be able to create python specific tutorials that are based on typical databases.  The handling of typical backend database configurations should be simplified.