Specs and fixes for DynamicPathVisualizer

DynamicPathVisualizer had a bunch of issues when dealing with non-SampledProperty properties; mainly because it had no unit tests associated with it and it's not a common use case (and I was lazy when I wrote it).  I added a bunch of tests and fixed problems they uncovered.  Path visualization still needs to be optimized/re-written in the future, but this will certainly improve things until that happens.