Modified XTend files to remove deprecated annotation @Property and replace them by @Accessors.
Merge branch 'develop' into migration-xtend_273
Added an anchor to Actors representations, allowing to create FIFOs without output port (the port is created afterward).
Modified LayoutActorFeature to prevent NPE when iterating anchors of an actor.
The anchor added to an actor to allow connections to start without a pre-existing output port does not have any GraphicalAlgorithm, and should not be considered when resizing an Actor.
Added an UpdateDiagramFeature allowing to update diagrams with new elements or properties.
It uses a diagram version property and methods updateFromVersionX which contain all the modification from one version to another.
updateFromVersion1 add a ChopBoxAnchor to each Actor in the Diagram, to allow starting a connection from an actor without pre-existing output port.

PiMMDiagramTypeProvider.isAutoUpdateAtStartup has been set to true, to allow update just after a Diagram has been open.

PiMMFeatureProvider.getUpdateFeature now returns the UpdateDiagramFeature when the context.getPictogramElement() is a Diagram.
Format.
updateVersion set hasDoneChanges to true if the version of the diagram is not the current one.
Changes done by the updateVersion method are thus taken into account and saved.
Merge branch 'PiMM-UI_create_connection_from_actor' into develop
Merge branch 'migration-xtend_273' into develop
Merge branch 'develop' of github.com:preesm/preesm into relativeConstraints
Problem of a cycle appearing in the DAG. Looking for solutions in the mapping of Relative constraints.
Debugging relative constraints. Changed the unmap/map strategy.