[446409] Change guides color for snapToShapes feedback.

This needs to duplicate the SnapFeedbackPolicy GEF class and to add this
new policy everywhere the old one is installed.

Bug: 446409
Change-Id: I3efb5893fc2356ac3f3c0609ab3af801c54b41df
Signed-off-by: Laurent Redor <laurent.redor@obeo.fr>