If we keep doing design validations at two different places, they can
only start to drift apart. Board Setup should validate for malformed
data ONLY; everything else is the business of DRC.
This also fixes a bug where implementation validations would not allow
OK in the dialog, but wouldn't put up a message to say why. We now use
the InfoBar impl from Jon's commit for that.
For some kinds of issues, we want a way to point them out but
we don't need to keep the user from being able to close the
dialog. A separate Validate button lets the user check for
issues if desired, but these issues are not "fatal" and can
be ignored if the user wishes.
Jeff Young
Jon Evans