Simu5G 1.3.1

This is a minor update for Simu5G-1.3.0. In addition to fixing regressions
in the previous release and making some cosmetic improvements, the main highlight
of this release is the revamp of the fingerprint test suite, which now provides
a more comprehensive safety net against future regressions. Changes in this
release were contributed by Andras Varga (OMNeT++ Core Team).

Changes:

• Example simulations: Marked abstract configs as such (abstract=true) in omnetpp.ini files
• FlowControlInfo's MacNodeId fields are now properly shown in Qtenv object inspectors
• Replaced EV_ERROR << lines with throwing cRuntimeError
• TrafficLightController: fixed startState NED parameter (also changed type from int to string)
• Fingerprints: CSV files merged into simulations.csv, added missing simulations,
  standardized on the set of fingerprints computed (tplx, ~tNl, sz), translated
  gen_runallexamples.py into Python and improved it

Fix regressions in v1.3.0:

• MECResponseApp: fixed wrong @class annotation
• BackgroundScheduler: fix "binder_ not initialized" error
• MecRequestForegroundApp, MecRequestBackgroundGeneratorApp: add back lost parameter defaults
• BackgroundCellTrafficManager: fix "Not implemented" thrown from getBackloggedUeBytesPerBlock()
• tutorials/nr/omnetpp.ini: fix missing unit for txPower parameter (dBm)