[435879] Reenable Begin operation creation as DiagramDescription child

Bug: 435879
Change-Id: I6ffe8b846216c7dc1f766a0664129d68362d29ea
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[435879] Reenable Dot style for Node mappings

Bug: 435879
Change-Id: I609cf0a6383f87f87b195babf1d18feacb47a5c7
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[435879] Disable SetEObject model operation from sirius.editor

It was previously done from sirius.editor.diagram.

Bug: 435879
Change-Id: I620ede63b9acdc9fec119d63138ab13b5b13938a
Signed-off-by: Maxime PORHEL <maxime.porhel@obeo.fr>
[427278] Use the official Eclipse Modeling icon

See https://wiki.eclipse.org/Modeling_Project_Releng/Plugin_And_Feature_Files#Branding_Icon_In_About_Eclipse_Dialog

Bug: 427278
Change-Id: I0576627e35998c37d665e182e19722038461d933
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
[436338] Use a "released" Orbit repo

Bug: 436338
Change-Id: I65de4bc4038c97807f3a17189fe8061e9b4741f4
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>