EventEdit: don't discard fields we don't handle and add a note about it.

src/EventEdit.tsx

@@ -106,7 +106,11 @@ class EventEdit extends React.Component {
       return;
     }
 
-    let event = new EventType();
+    let event = (this.props.event) ?
+      this.props.event.clone()
+      :
+      new EventType()
+    ;
     event.uid = this.state.uid;
     event.summary = this.state.title;
     event.startDate = ICAL.Time.fromString(this.state.start);
@@ -204,6 +208,11 @@ class EventEdit extends React.Component {
               secondary={true}
             />
           </div>
+
+          <div>
+            Not all types are supported at the moment. If you are editing a contact,
+            the unsupported types will be copied as is.
+          </div>
         </form>
       </React.Fragment>
     );

src/pim-types.tsx

@@ -27,6 +27,10 @@ export class EventType extends ICAL.Event {
     comp.addSubcomponent(this.component);
     return comp.toString();
   }
+
+  clone() {
+    return new EventType(new ICAL.Component(this.component.toJSON()));
+  }
 }
 
 export class ContactType {