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

rm direct python include (CorePython.py) from libBornAgainCore.i: we use the CMake/plot_utils machinery instead.

Merge branch 'testing' into develop: persistence testing framework for Py examples (still to be filled with actual testing); removed dependence on matplotlib from plot_utils, from exported scripts, and from covered Examples.

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.

plot_utils no longer requires matplotlib (import moved into DefaultFitObserver::__init__. This resolves #1576.

All simulation examples now take argument -p or filename. All fitting examples are taken out from the persistence tests. All persistence tests pass, but they do not yet test persistence.

Simplified auto-generated scripts from ExportToPython; prepared first Python Example for coverage by new functional test.

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

CMake configuration basically ready for Examples persistence tests; unit tests temporarily disabled.

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.