Improve RelationMapBuilder so it creates reusable queries

[fkleedorfer]

Problem description

The RelationMapBuilder is used to create SPARQL on the fly, which is helpful but not as efficient as it could be. A rework would be good.

Preferred solution

No response

Are you interested in contributing a solution yourself?

Yes

Alternatives you've considered

No response

Anything else?

I already have that, will open a PR to contribute it.