Bug 399023 - Add a p2 repository for assembling client bundles

This is required to consume the result of the orion client build from
the orion server build which runs in a different Hudson job since Tycho
can only consume bundles from another build via a p2 repository.

Assembling bundles directly into a p2 repository requires that we update
to use Tycho 0.17.

Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>