Add a message to let the user know when the synchronization is beign run
in simulation mode.
All the echo's are removed insted of just throwing everything to stdout
the class is now capable of sending it's output to any logging system.

* The Logger class is added. It can be inherited to allow the class file
  synchronization class to log it's output to any logging system the user
  wants, such as a database or a PHP logging facility like apache's
  log4php.

* The debug_mode attribute is removed from the file synchronizer, it will
  now log it's output to the given logger (if any) or else will run
  silently.