Options for user: choosing header type

[ChristineHaugen-aut]

Two types of metadata headers are available for cim graphs: MD (http://iec.ch/TC57/61970-552/ModelDescription/1) FullModel and DCAT (http://www.w3.org/ns/dcat) Dataset.
Both the parser and the serializer should allow the user to choose which header to use for the graph. That requires implementing a switching system.

Options the user should have:

1. Leave it as it is in the source file or specify which one to use.
2. If the header is specified but don't match the header in the source file:
   • The header is collected from a manifest file.
   • If the manifest file is not provided, a fall back will be implemented where the new header is reconstructed from the old by switching predicates, objects and namespaces. This must be hardcoded, and will therefore be vulnerable to future changes made in the metadata formats.

These options will be available both in the parser and the serializer, thereby allowing bidirectional switching between file formats (ex. both CIMXML to trig and trig to CIMXML conversion will be handled smoothly).