Extend Config class with fields

[plaos]

Currently, we read the config file into a raw dictionary. This leads to needing to explicitly extract fields by subscripting, in order to be ergonomic. Example: user = config["user"]. This isn't very nice, instead we should create fields on the Config class. This may involve restructuring the current pattern a bit, as the Config class today is mainly a namespace for setup and retrieval of the config file. The get_configuration method should probably be removed, in favor of just accessing the (new) fields directly, for instance.