[releng] Update and improve releng scripts

* Version upgrade for Tycho, CBI JAR Signer and the Eclipse version
  used during the publication.
* Only keep the 5 most recent entries in the composite repos.

Change-Id: I389b6732210d3085e96703827134e778094758b3
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
2 files changed