Code architecture improvement: socket IO

[c8y3]

Code related to socket IO could be grouped, since event handlers and emitters are part of the public API of the backend.

The proposition is to:

• group all methods with annotation @socket_io.on in namespace app.blueprints.socket_io_event_handlers
• decide some namespace and group all methods which call socket_io.emit in it (maybe app.iris_engine.socker_io.emitters? I am unsure what the app.iris_engine namespace is supposed to represent/contain)