[releng] Switch to tycho 2.7.5
- remove duplicate keys in in feature:
  org.eclipse.emf.ecore, org.eclipse.papyrus.infra.viewpoints.policy, org.eclipse.emf.transaction
- remove all esf plugins from required plugins

Change-Id: Icc78fe8ae44f6c4b7a9f8946a98a801523f78b73
Signed-off-by: aradermache <ansgar.radermacher@cea.fr>