Add information from DataCite API regarding a Datasets relation to other Datasets and it's resource type
add the following info from DataCite to the DataMetadataDict (representation of a Dataset Publication):
- Resourcetype (e.g. 'Dataset', 'Software'etc.), closes #28 (closed)
- RelatedIdentifiers (recording relations to other Dataset publications like e.g. 'IsPartOf', 'IsVersionOf' etc.), closes #10 (closed), closes #11 (closed)