Support alternative hardcoded values

[RickMoynihan]

(construct-1 ?label-or-title [[:resource #{:rdfs/label :dcterms/title} ?label-or-title]])

[RickMoynihan]

This is similar to #9 but slightly more constrained to only compile time syntax. Supporting both runtime and compile time cases would be preferable; but this is perhaps more common than the runtime case. i.e. it would be preferable to do #9 to this ticket; but if #9 proves awkward this would an improvement too.