Added TudeySceneModel.Entry.getReferenceType()

Provides the generic type argument of the ConfigReference
returned by getReference().
Oh, that was a nice description.
Begin modifying the ConfigSearcher to know the types of refs.
Comment out "experimental" (unused) findPath.

Also changed AttributeDetector to return a Multiset.
Further progress; everything uses findAttributes().

Changed the gui to only accept an AttributeDetector<Presence>,
but perhaps I can smooth that out...
Avoid creating HashMultisets unnecessarily.

...at the cost of a bit of code-weirding.
Made the gui more generic.

Added a SearchReporter interface that combines an AttributeDetector
with a way to format the results to a label.
Fix javadoc error.