Sketch Dimension refused a dimension the sketch couldn't take, with
"that dimension would over-constrain the sketch; add it as a driven
(reference) dimension with driven: true", which the tool gave no way to
do. It now places it as a driven dimension instead: while placing, the
preview shows it in parentheses in the driven colour, and the click adds
it at once (it has no parameter and no value to edit), with a status line
saying why. Other refusals, such as an unsupported pick, are reported as
before, since the driven dimension is refused too.
Refs #320
Co-authored-by: Vitali M. <[email protected]>
