Merge remote-tracking branch 'origin/release_1.21.0' into develop

Conflicts:
	examples/org.eclipse.emf.ecp.makeithappen.view.group.renderer/META-INF/MANIFEST.MF
	releng/org.eclipse.emf.ecp.repository.target/category.xml
	tests/org.eclipse.emf.ecp.ide.util.test/META-INF/MANIFEST.MF

Change-Id: Ic55917318de72f701bbe78282884aefa92094b5d
Signed-off-by: Eugen Neufeld <eneufeld@eclipsesource.com>