plugin XEP-0166: refactoring, and various improvments: - add models for transport and applications handlers and linked data - split models into separate file - some type hints - some documentation comments - add actions to prepare confirmation, useful to do initial parsing of all contents - application arg/kwargs and some transport data can be initialised during Jingle `initiate` call, this is notably useful when a call is made with transport data (this is the call for A/V calls where codecs and ICE candidate can be specified when starting a call) - session data can be specified during Jingle `initiate` call - new `store_in_session` argument in `_parse_elements`, which can be used to avoid race-condition when a context element (<decription> or <transport>) is being parsed for an action while an other action happens (like `transport-info`) - don't sed `sid` in `transport_elt` during a `transport-info` action anymore in `build_action`: this is specific to Jingle File Transfer and has been moved there rel 419