Critical fixes to the SPD cluser code:

Critical fixes to the SPD cluser code:

- Removed DefineOutput from default CTOR - this CTOR is only used by ROOT I/O
  system, and _must_not_ set up things, as the data will be set via the
  streamer.
- Make all Getters of manager const.
- Moved implementation of manager class member functions to .cxx file.
- Removed direct setters/getters from task.
- Check pointer validity before de-referencing.
- Cache (in a static) return string from GetFileName - if not static,
  the data pointed to could disappear and lead to very strange errors.
- Fix includes and wrong cast in AliCentraldNdeta.cxx
- Also generate dictionary AliCentralMultiplicityTask::Manager - otherwise
  objects of that class is not persistent.