add an example showing usage and benefits of QOnEvent

This example shows how to use QOnEvent.

- Two data grids are rendered (100 rows). One uses event delegation
the other one row actions and a control proxy.
- The lines of JavaScript rendered are compared.
  The event delegation version uses 11 lines of JavaScript
  the other version ~900!
- dynamically adding children without the need to add actions
  when delegation is used is shown. (add person button that adds
  a row via JavaScript ==> event delegation version: hover effect, delete button
  clicking is working without adding another action)