Preesm Release 2.4.0

The last version of Preesm introduces the long awaited copy/paste in the PiMM editor. Along with this convenient feature, this version fixes several bugs in the UI (error popups, autolayout crash, …). Complete list of changes is available in the release notes. Binaries are available on Github and already existing Eclipse installations can be updated using the Preesm update site. Also, although we did not test it thoroughly yet, Preesm works within latest Eclipse Oxygen.