SpinSlider and ScrollSpinBox read-only support

PIVariantEdit - support for read-only for all types
PIValueTreeEdit - drop Parent grouping, default now Groups, full grouping control, global read-only support, fix new label error

libs/widgets/spinslider.cpp

@@ -50,6 +50,13 @@ bool SpinSlider::adaptiveStep() const {
 }
 
 
+void SpinSlider::setReadOnly(bool r) {
+	m_read_only = r;
+	spin->setReadOnly(r);
+	slider->setEnabled(!r);
+}
+
+
 void SpinSlider::setAdaptiveStep(bool on) {
 #if (QT_VERSION >= QT_VERSION_CHECK(5, 12, 0))
 	if (on)