Refactoring of the ThrowableProxy class.

ThrowableProxy now implements the IThrowableProxy interface as shown below:

public interface IThrowableProxy {
  public String getClassName();
  public String getMessage();
  public ThrowableDataPoint[] getThrowableDataPointArray();
  public int getCommonFrames();
  public IThrowableProxy getCause();  <-- Joern smiles
}

Instead of being a flat structure, ThrowableProxy now contains nested
exceptions (cause) as a nested ThrowableProxy references. This was
requested by Joern Huxhorn on several occasions.

Classes printing threads had to be modified as a result of this
refactoring. 

The ILoggerEvent interface has also been slightly refactored. The
LoggerRemoteView class is no longer referenced. Instead the
LoggerContextVO class is used. As a result, serialized events are
larger by a few bytes, but the code is hopefully much clearer.

In response to comments from the dev mailing list, the LoggingEventSDO
class has been renamed as LoggingEventVO.