- Change the synchronization code so that the
changelog server can now be used directly through the ChangelogBroker class
as a client API.

This is very usefull for testing because it allows to generate a wide variety of events
and therefore helps to test code that is otherwise rarely used and therefore difficult
to tests like :
   .starting condition.
   .conflicts resolution.
   .tests of error conditions.
   .fail-over tests.

- add the first set of tests for the currently available conflict resolution code.

- fix the two bugs (772 and 773) discovered when coding these tests.