[439871] Avoid dependency to GMF Runtime for a simple geometric computation

Duplicate the code from BaseSlidableAnchor.getAnchorRelativeLocation()
directly into FixBendpointsOnCreationCommand so that the bundle does not
depend on org.eclipse.gmf.runtime.draw2d.ui just for these few lines of
simple code.

Bug: 439871
Change-Id: I14cc63328eb832e6be7db89c7be0c7c4264fdc0c
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
[439871] Move 3 plug-ins from runtime.ide.ui into the runtime feature

The oes.diagram, oes.diagram.layoutdata and oes.ext.gmf.notation do not
depend on the UI, and can thus be part of the core feature.

Bug: 439871
Change-Id: I2d7cf3f38fcebc5d2f9c531a458328201ec4d764
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
[439871] Add a new update-site for headless-compatible features

The new update-site is a subset of the full one, with only the features
that do not depend on the UI.

Bug: 439871
Change-Id: I40374facf74634c13ce3219b0d0624837bbb3bbc
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
[439871] Split the modules list  into "headless" and "full" profiles

This does not change anything to the build as both profiles are active
by default and use the same full Target Platform, but is another step
towards a headless build by clearly separating the modules (plug-ins and
features) which should work in headless mode from the rest.

Bug: 439871
Change-Id: I35405de9d6166ef38d7c2af93796aa8f12ed1cde
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>
[439871] Add new headless target platform

Based on Luna only for now, it contains the minium required stuff to
build all the modules in the "headless" profile and produce the
oes.headless.update repository.

The new platform is used when the "headless" profile is enabled and the
"full" profile is not. From the command-line, a headless build can be
invoked with:

  % mvn -P!full clean package

Note that you may need to escape the "!" character with "\!" depending
on your shell.

Bug: 439871
Change-Id: Ide46b33393f7e3c6c57c12938153cb44a9eef293
Signed-off-by: Pierre-Charles David <pierre-charles.david@obeo.fr>