Returns a 0/1 value corresponding to function object trigger levels.

    Usage:
    \verbatim
        <entryName> functionObjectTrigger;
        <entryName>Coeffs
        {
            triggers        (1 3 5);
            defaultValue    false;  // Default when no triggers activated
        }
    \endverbatim

ENH: add reset() method for Constant Function1

ENH: allow forced change of trigger index

- the triggers are normally increase only,
  but can now override this optionally