Reactivate on change for background layer

src/fields/number.jsx

@@ -4,6 +4,7 @@ import { Select, Input } from 'rebass'
 /*** Number fields with support for min, max and units and documentation*/
 class NumberField extends React.Component {
 	static propTypes = {
+    onChange: React.PropTypes.func.isRequired,
 		name: React.PropTypes.string.isRequired,
     value: React.PropTypes.number,
     default: React.PropTypes.number,
@@ -15,6 +16,7 @@ class NumberField extends React.Component {
 
 	render() {
 		return <Input type="number"
+			onChange={this.props.onChange}
 			label={this.props.name}
 			name={this.props.name}
 			message={this.props.doc}