#1264 Fix language equivalence check for differences wrt initial locations + some other improvements

• Best to review per commit.
• End-user visible changes:
  • Event-based language equivalence check: fixed for the only difference being in marking of initial locations, or language from initial locations. Previously, this was not detected.
  • Event-based language equivalence check: improved the output in case the counter example concerns a pair of initial states.
  • Event-based language equivalence check and DFA minimize: improved readability of partitioning blocks printed as part of debug output.
• Other changes:
  • BlockLocation and Event now have a custom toString method for easier debugging.
  • CounterExample:
    • Asserts in constructor that its path is never null. No more handling null path in LanguageEquivalenceCheckApplication.printPath.
    • JavaDoc improvements.
  • org.eclipse.escet.cif.eventbased: Use autIdx instead of autNum.
  • LangEquivCalculation:
    • constructCounterExample improvements:
      • Comment improvements.
      • Add assert to check for exactly two automata, before using this fact.
      • Moved newLocs declaration a bit down, to section where it is used.
      • Don't swap locs and newLocs, but set their values explicitly.
      • Iterate with pathIdx instead of i.
      • Renamed numEventsEnabled to numAutsEnabled.
      • Split the method into two methods, to allow re-using the end of the method (used in fixing the bug).
    • getReversePath improvements:
      • Comment improvements.
      • Swap a comparison to be similar to earlier one (+ easier to read).
    • getSplitExplanationPath improvements:
      • Moved method, so that methods are in invocation order.
      • JavaDoc/comment improvements.
      • Use Assert.areEqual instead of Assert.check.
      • Handle the three possibilities in order.

Closes #1264 (closed)