Bug 581890: [Sirius][ComponentDiagram] Fix test implementation and VSM

- Remove assumeTrue from tests
- Rename RECONNECT_TARGET__COMPONENTREALIZATION__TOOL into
RECONNECT_TARGET__COMPONENT_REALIZATION__TOOL (uniform this rule for
other component reconnection tools),
- add javadoc on test methods,
- uniform label API on all mappings,
- update default weight/height of Mode Package style.

Bug: https://bugs.eclipse.org/bugs/show_bug.cgi?id=581890
Change-Id: Ic5ccceb9685000000c10f4ce8b7f0b6eebaedbf0
Signed-off-by: Jessy Mallet <jessy.mallet@obeo.fr>