Persistence test now able to read multiple data and reference files; detects missing data and reference files.

We do not want a sys.path=... command in each example. Therefore in PyPersistenceTest the system call of Python must be preceded by a setting of PYTHONPATH.

Resolving #1440: CMake part done. C++ part half done. Still TODO: (C++) compare with reference (Py) modify all examples

PyCoreTest now writes concise log lines, and by some miracle Python errors also appear in the log. This resolves #1571, except for a possible failure to detect zero-filled detector images.

Python script, generated by ExportToPython, now takes argument '-p' for plotting, or <output_filename>. This resolves #1573.

Merge IFunctionalTest::analyzeResults() into IFunctionalTest::runTest() [Tests are a sequence of actions, each of which may result in failure. Therefore there is no natural division between test and analysis]. Also detect errors from Python script execution commands. This partly resolves #1571.

more explicit method name "simulationToPython"; change parameter name into "simulation_output_filename" to make clear this is the output filename of the simulation, not the output filename of the export method.

prepare for refactoring Python export; simplify OrderedMap -> LabelMap, and move it to where it is used

mv PyCore/suite/PySuiteTest.cpp -> PyCore/suite/PyCoreTest.cpp; wrote or improved class header comments in Test/Functional

On failed CoreFutest, print location of simulated image and of reference, and point to inspection tools. This solves the last open subissue of #1291.