Make sure to update rsb simultaneously.

also reduced verbosity for python and fixed the c++ test build settings

A new dedicated MessageConverter was added at the same time.

Important: Java version does not yet contain
  Messages (or Retraction, for that matter)
Note: Messages are received and routed to the
  handlers with the special new MESSAGE event
  type, as opposed to ADDED. This decision is
  of course open for discussion.
Additional bugfix: Typecasting conflict in C++
  payloads fixed. Reverted to cstdlib casts
  to avoid bulky exceptions being thrown.

Important: Java version does not yet contain
  Messages (or Retraction, for that matter)
Note: Messages are received and routed to the
  handlers with the special new MESSAGE event
  type, as opposed to ADDED. This decision is
  of course open for discussion.

Implemented retraction handler. Replaced deprecated converter repository call.