Add some documentation for the OpenMP mode, either from a user or from a developer point of view. Note that the part on the
OPENMP_AWARE flag is not written, because this has still to be done. Marcel said that Dan may have the time to implement that
Addition of a test checking the consistency of the results with multi-threading. A quite decently complex
network is covering almost all the templates, and simulations results are carefully compared without OpenMP,
with OpenMP and 1 or 2 threads.