attributeDeviceDisplayWidget.py: fix bug with soft limits
add a limit check on the GUI value before updating the attribute.
Previously the limit check worked only when the user clicked on up/down arrows (see kamzik3.gui.attributeDisplayWidget.AttributeDisplayWidget.__add__
and __sub__
), but it was still possible to enter manually a value out of limits.
Implemented and tested during the beamtime, works fine.