Validation now skiped if Linking isn't done yet and unresolved proxy are
enountered.  This avoids certain problems I've seen on the Console, and
is probably a bit faster, too.
Minor optimization (plus minor changes)
new test (green) for Validations. Unfortunately the problem I'm after
only seems to appear in-IDE/UI, not in a test.. :-(
FIXED double validation error / marker problem.  Gave up on getting a
test for it working.