Make TestCase independant of Filesystem capability to set readOnly

Use a ResourceChangeListener to make the test fail if a file which
was explicitely marked as readonly ends up being modified.
Add a warning in SiriusDiagramTestCase that readonly might not be
supported on the FS.
[cleanup] Add .DS_Store file to .gitignore

The file is generated by Mac OS™.

Change-Id: If604f9a01a3a0d93e954536c6c162427099d18ec
Signed-off-by: Maxime Porhel <maxime.porhel@obeo.fr>
Make TestCase independant SiriusDiagramTestCase.setReadOnly
[442289] Rename distribute actions

* Distribute With Uniform Gaps Horizontally --> Distribute Gaps
Horizontally
* Distribute Centers Evenly Horizontally --> Distribute Centers
Horizontally
* Distribute With Uniform Gaps Vertically --> Distribute Gaps Vertically
* Distribute Centers Evenly Vertically --> Distribute Centers Vertically

Bug: 442289
Change-Id: Ia7382bd43f963fcfda7f41b3ce12ce601ec7c122
Signed-off-by: Laurent Redor <laurent.redor@obeo.fr>
[432982] Revert test added before merging corresponding fix

This test will be added again in the corresponding review
https://git.eclipse.org/r/#/c/33886/

Bug: 432982
Change-Id: I218f82bfdf7082bf3ec414a6b83c16704c28b708
Signed-off-by: Laurent Redor <laurent.redor@obeo.fr>