[Chatbot] Add two-way communication

[yuripourre]

Currently there is no way to register a listener when user needs to give more details or answer a question back.

One approach would be adding a register to the outcontext, so the parsers can add those "answer interceptors" to a priority queue.

Basically those interceptors have priority and if the answer is not given on time (or invalid) they are removed to the query.

In case they are valid we need to call the original source back and inform the decision.