Provide node expansion via shapes and pluggable widgets.

[rob-metalinkage]

A range of cases require expansion of objectProperty values as inline nodes in the presentation. A general mechanism should be introduced and used for special cases: e.g. a skos:narrower or skos:member widget

The mechanism should implement the necessary subset of SHACL (i.e. attachment of NodeShapes to either object types or to the specific property of the focus object type.

A default widget for blank nodes should be defined that allows "toString" patterns by node type.

Some common widgets should be available by default for the VocPrez profile - for example PROV, PROF and FOAF nodes