Testsuite fixes for cross-platform test passing

This doesn't really need a formal review, since it doesn't actually alter working code. I'm just used to posting pull requests for everything I do.

This polishes the scripts in control of the testsuite, widens some of the test error tolerances, and updates some of the reference output, with the goal of making tests pass across multiple platforms with different compilers and math libraries that sometimes make tiny image differences even though they are a visual match. In some cases, I'm also compensating for updated dependent libraries (example: different versions of Partio sometimes will retrieve the same set of points from a query, but in a different order).