[FEATURE] Add a configuration template for mapping XML to Python objects

[RadovanTomik]

Brief description. In order for this application to be as robust as possible we need to provide an easily customizable map for parsing objects from XML files. E.g.

{
patient_map: {id: "patient.@id", gender: "patient.@sex"},
sample_map: {id: "**.STS.material.@id"}
}

The path syntax should be compatible with glom. Desired functionality acceptance criteria

• [x] The map is passed as a dict to the XMLrepository class.
• [ ] The map can be loaded into the docker container as a json file.
• [ ] If no map is found then a default one is used.