In Sequence Diagram, improve ReorderTool to allow lifeline change

[peransin-obeo]

When drag-n-dropping node in Sequence Diagram, it is possible to change elements order but not elements lifeline even if gef/gmf provides indication to do so.

These are the step to introduce this feature:

• Add variables 'beforeContainerView' and 'afterContainerView' in tool property
• Evaluates such variables in
  

  sirius-desktop/plugins/org.eclipse.sirius.diagram.sequence/src/org/eclipse/sirius/diagram/sequence/business/internal/operation/SynchronizeISequenceEventsSemanticOrderingOperation.java

  Line 137 in 03aee7f

  private void updateSemanticPosition(ISequenceEvent eventToUpdate) {

• if values are different apply this sequence:
  

  sirius-desktop/plugins/org.eclipse.sirius.diagram.sequence/src/org/eclipse/sirius/diagram/sequence/business/internal/operation/SynchronizeISequenceEventsSemanticOrderingOperation.java

  Line 182 in 03aee7f

  applySemanticReordering(semanticElement, startingEndPredecessorAfter, finishingEndPredecessorAfter, reorderTool);