- pre-operation plugins are not called anymore when processing synchronization operations
  for ADD,DELELTE and MODIFYDN as it was already the case for MODIFY operation
  This is necessary to make sure that entries use the same unique ID everywhere.

- Synchronization now its own serialization mechanism for synchronization messages
  (before it was using java object serialization)
  This allows to use the same serialization for data transfer between LDAP servers 
  and changelog servers and for saving the changes into the changelog database.
  It will also allow to make some evolution the protocol without breaking the compatibility
  with previous releases.
  This also brings some performance improvements as this new serialization mechanism
  only needs to be done once on the master that originally processed 
  the operation while before it was done for each transfer over the wire and for writing
  the changelog database.