Add ad-hoc query builder in Connect

Users need to be able to create ad-hoc queries. The builder should be visual and cover a significant portion of the semantic abilities of SQL (though need not be based on SQL nor generate that syntax, per se) - "SELECT" flexibility, no limitation on number of "JOIN" steps across Groups, Models, Objects, Object Occurrences, Connections, Connection Occurrrences, etc.

The UI should be space-efficient.

Something similar to the visual approach used by Access would be acceptable. Alternatively a tree-based approach can also work as long as key query semantics are accounted for.

Should include more elaborate filters like objects with attribute X AND attribute Y NOT MAINTAINED.