Implement an HTTP Service based on Tornado

[tcalmant]

It seems possible to implement an HTTP service using Tornado.
This should increase the performances of Pelix HTTP (Tornado is faster than the HTTP server from the standard library).
It should also bring new features like websockets support.

An experimental implementation could be written before the release of 0.6.3.

[tcalmant]

Ideas:

• Use a "proxy" request handler, to map the iPOPO servlet API to Tornado. This will allow to use existing servlets without additional work.
• Public a "tornado" service, so that iPOPO component can register their Tornado handler
• Handle the whiteboard pattern for Tornado handlers ("tornado.handler.factory" services ?)

Support of Tornado request handlers will allow to use the native features of Tornado.

Steps of development:

• Write a main component to start/stop the Tornado server and publish the "tornado" service
• Write test request handlers and register them with the "tornado" service (first unit tests)
• Handle the whiteboard pattern to detect the request handlers (+ unit tests)
• Write the servlet API proxy (+ unit tests)

[tcalmant]

As it depends on Tornado, which is not a "basic" dependency, this feature should be implemented in a side project.