Adding at interface IAnnouncer overloading of Error method.

Adding at interface IAnnouncer overloading of Error method, that it has
an exception for argument.
Adding at abstract class Announcer basic implementation of Error method

It will visit the entire tree exception until the exception is non-NULL
and prints its contents by calling the Error.
Replace announcer.Error(string message) with announcer.Error(Exception exception)
Add at CompositeAnnouncer Error(Exception exception) implementation
Merge pull request #543 of spaccabit/Issue-483

  Add at CompositeAnnouncer Error(Exception exception) implementation
  Replace announcer.Error(string message) with announcer.Error(Exception exception)
  Adding at abstract class Announcer basic implementation of Error method
  Adding at interface IAnnouncer overloading of Error method.