Add missing plugins for ELK
diff --git a/plugins/org.polarsys.chess.diagramsCreator/META-INF/MANIFEST.MF b/plugins/org.polarsys.chess.diagramsCreator/META-INF/MANIFEST.MF
index e9620ce..d068b11 100644
--- a/plugins/org.polarsys.chess.diagramsCreator/META-INF/MANIFEST.MF
+++ b/plugins/org.polarsys.chess.diagramsCreator/META-INF/MANIFEST.MF
@@ -31,7 +31,14 @@
  org.eclipse.papyrus.uml.diagram.common,
  org.eclipse.papyrus.uml.tools,
  org.eclipse.emf.transaction,
- org.eclipse.papyrus.infra.services.openelement
+ org.eclipse.papyrus.infra.services.openelement,
+ org.eclipse.elk.alg.disco,
+ org.eclipse.elk.alg.force,
+ org.eclipse.elk.alg.graphviz.dot,
+ org.eclipse.elk.alg.graphviz.layouter,
+ org.eclipse.elk.alg.mrtree,
+ org.eclipse.elk.alg.radial,
+ org.eclipse.elk.alg.spore
 Bundle-RequiredExecutionEnvironment: JavaSE-1.8
 Bundle-Vendor: Fondazione Bruno Kessler
 Import-Package: org.apache.log4j