Fix SpinBox to have a default locale-aware DoubleValidator

The validator is only pertinent when a SpinBox is editable acting only
on the text string input and does not affect the SpinBox's
value-based from: and to: limits.

components/controls/SpinBox.qml

@@ -167,6 +167,13 @@ CT.SpinBox {
 		}
 	}
 
+	validator: DoubleValidator {
+		locale: root.locale.name
+		bottom: Math.min(root.from, root.to)
+		top:  Math.max(root.from, root.to)
+		notation: DoubleValidator.StandardNotation
+	}
+
 	Timer {
 		id: pressTimer