Add keys for linking patterns (for QC & visualisation)

STATUS: Draft

Proposal for linking DOSDP patterns for QC/constraints (metamodelling) & for visualization of pattern relationships. Note: this does not mean inheritance of axioms.

* parent/child relationship
* Child patterns should have or extend the vars in the parent pattern.
* Range of vars may be further restricted in the child pattern

* disjoint_with: There should be no OWL class that 'conforms to' both the pattern and a pattern declared disjoint_with it. The meaning of 'conforms to' is not specified in dosdp tools (this is left to implementers to decide), but practically refers to matching via the DOSDP_tools query system matching only on EquivalentTo statements.

Keys to add:

parent_pattern: the pattern_name (better to use IRI?) of a single parent pattern.
disjoint_pattern: the pattern_name (better to use IRI?) of a single(?) disjoint pattern

No files, tests, or entry points are named in the issue. First review how DOSDP pattern keys are currently specified and consumed, then resolve the open choices around parent and disjoint pattern identifiers and cardinality; done means the keys and their semantics are defined and supported consistently.

Written by the indexing model from the issue text.