[cleanup] Avoid potential NPE in ViewEdgeFigure

AbstractDiagramEdgeEditPart.ViewEdgeFigure has 2 methods (paintFigure
and paintChildren) which try to access the Sirius model (the DEdge) in
order to decide if it is visible (and thus should be painted or not). In
some circumstances, a Draw2D deferred layout can trigger these methods
in a state where the models and edit parts are invalid, and in that
situation, the call to resolveSemanticElement() breaks with an NPE in
TransactionImpl.commit().

The fact that ViewEdgeFigure (from the Draw2D layer) has access to the
edit part and tries to read the model is clearly broken in itself. In
the case of paintFigure and paintChilren, it is probably not even needed
because the visibility is normally propagated the other way around (i.e.
from the DEdge model element towards the Draw2D figure). I'll open a
ticket to remember to clean this up in the future, but in order to
minimize the changes in the context of a maintenance branch the guard
which is already present in the layout() method will do:

    if (!isActive()) {
         return;
     }

Change-Id: I1f79c2dae650593e10e211a383421caec8e5faa8
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
[439140] Enable  all representation creation menu from edges

Bug: 439140
Change-Id: I53ab38e6a0370fba733cbcb4879a25eedd906522
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[439140] Improve representation creation menus computation

. In Diagram, remove duplicated code
. In Diagram, Table, Tree: check if the representation to create is
define in an active Viewpoint, and only if it is true, evaluate the
precondition if not empty.

Bug: 439140
Change-Id: Ibe8e9e2ba44af69c497f76188642ed73af576dad
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[439140] Improve Navigate menu computation

 . Rename isFromSirius into isFromViewpoint
 . Compute the current session only once for the new details menu
computation
 . Check that description reference by
RepresentationNavigationDescriptions is defined in an active Viewpoint,
and only of true, evaluate the precondition (if not empty)

Bug: 439140
Change-Id: I8f2d924bc21a0d2f48942aa5e39d94e17eb50fd2
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[cleanup] Set the name to the correct variable

At creation, set the container variable name to container and the
containerView variable to containerView.
We should maybe change the name multiplicity to [1..1].

Bug: 439140
Change-Id: Ife3fc0f09935ed75f857f454a3982ee410d9811c
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[cleanup] Compute subdiagram decorator with activated Viewpoints only

Bug: 439140
Change-Id: I16818ad31c101dbee46d5dc197857d0b75f6b1c6
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[439210] Remove the default editor choice for ecore

Cloned and reported from 438808

Bug: 439210
Change-Id: If8b0505eea67b3ae26fc98e65c735f7be9285f13
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>