API change: EventAdmin

- The Event bean is removed
- The handle_event(event) method is replaced by a handle_event(topic,
  properties) method
Json-RPC: errors with jsonrpclib

- JSON-RPC doesn't work well with the available version of jsonrpclib
- I made a working version, which will be available soon on GitHub
Added a Dispatcher Servlet component

- Provides an access to the description of the exported services
- Responds in JSON format
- Accepts two paths:

  /endpoints: retrieves all endpoints
  /endpoint/<uid>: retrieves the description of the given end point
Multicast discovery uses the dispatcher servlet

- Multicast datagrams contains the minimal required information only
- An "access" entry indicates where to access the dispatcher servlet,
  which contains the whole endpoints descriptions
RemoteService: Exported specifications are now filtered

The "service.exported.interfaces" property is now checked to filter the
specifications to export.
If a component exports multiple services and uses this property, only
the specifications indicated in the property will be visible by the
remote peer.