EventAdmin: Late handler lookup
EventAdmin: Late handler lookup

- Only service IDs are kept while prepare an event propagation
- EventHandler services are retrieves at notification time
  => Avoids errors if a remote event handler is gone before the notification proceeds
- Now using the BundleContext instead of iPOPO to find event handlers
- Removed the @Requires, Bind, Unbind decorations

ahmadshahwan/ipopo,ahmadshahwan/ipopo,tcalmant/ipopo