Insert OboGraph functionality from ARCValidation

[omaus]

ARCValidation library has functions to transform OboOntology type into respective FGraph (from Graphoscope). Move that from there to this repo but in its own project (FsOboGraph).

See also nfdi4plants/arc-validate#56

[kMutagene]

@omaus do you want to tackle this next after #32 is done?

[omaus]

@kMutagene Yeah, sure. 😃

[omaus]

Additional:

• either CvTerm instead of OboTerm as NodeData or (maybe even better) Accession or (maybe best) OboTerm option
• generalize TermRelation (if needed)
  • needs equivalent relationship but ONLY applies if in document header xrefs are treated as equivalent

[kMutagene]

(maybe even better) Accession

make sure to change the Node Key to the accession though