warnings/proptypes: use oneOfType to support object and string

src/components/Widgets/ControlHOC.js

@@ -8,7 +8,10 @@ class ControlHOC extends Component {
   static propTypes = {
     controlComponent: PropTypes.func.isRequired,
     field: ImmutablePropTypes.map.isRequired,
-    value: PropTypes.node,
+    value: PropTypes.oneOfType([
+      PropTypes.object,
+      PropTypes.string,
+    ]),
     metadata: ImmutablePropTypes.map,
     onChange: PropTypes.func.isRequired,
     onValidate: PropTypes.func.isRequired,

src/components/Widgets/DateTimeControl.js

@@ -19,5 +19,8 @@ export default class DateTimeControl extends React.Component {
 
 DateTimeControl.propTypes = {
   onChange: PropTypes.func.isRequired,
-  value: PropTypes.object, // eslint-disable-line
+  value: PropTypes.oneOfType([
+    PropTypes.object,
+    PropTypes.string,
+  ]),
 };