All three methods of this interface have changed to take a Message
argument instead of Object. This has motivated changes in all classes
that implement this interface (including unit tests and trailblazer).
The concept of 'current object' has been introduced (see ActionUtils
class in org.jboss.soa.esb.actions).
Existing action processors that used to take an Object argument, now
get it from their Message argument, operate on it, and put whatever
they determined is the new 'current' object into the Message they
return.
As we stand today, all action processors process method return the same
Message they received as argument; this circumstance would suggest that
the method could be void. That choice would however impede the
possibility of changing message implementation in the middle of an
action processing pipeline.
