The folder button handler works will for footprint libraries but we
needed a specific class for the schematic libraries as well.
Fixes: lp:1818346
* https://bugs.launchpad.net/kicad/+bug/1818346
Don't beep when inserting character from focused grid cell (but
before editor is opened).
Handle reference validation separately from name validation and
separately from user field value validation. The old way of setting
the fieldId on the validator wasn't working because the validator
gets copied.
Run validation when leaving cell. Don't just check for empty
(particularly for fields that CAN be empty).
Fixes: lp:1782917
* https://bugs.launchpad.net/kicad/+bug/1782917
(cherry picked from commit 79e04de)
Seth Hillbrand
Jeff Young
Baranovskiy Konstantin