Those two fields are present in the vector layer properties. It
was possible to set a minScale bigger than the maxScale.
Now, the maxScale is forced to minScale if the user tries to
set it to a lower value.
Rationale:
- there was a lot of large objects passed by value, so potentially
there's a speed bump from this
- even for implicitly shared classes like QString/QList there's still
a (small) cost for copying the objects when there's no reason to
- it's the right thing to do!
