Migrate the MVP into kotaemon (#108)

- Migrate the MVP into kotaemon.
- Preliminary include the pipeline within chatbot interface.
- Organize MVP as an application.

Todo:

- Add an info panel to view the planning of agents -> Fix streaming agents' output.

Resolve: #60
Resolve: #61 
Resolve: #62

tests/test_composite.py

@@ -30,6 +30,7 @@ _openai_chat_completion_response = ChatCompletion.parse_obj(
                     "finish_reason": "length",
                     "logprobs": None,
                 },
+                "logprobs": None,
             }
         ],
         "usage": {"completion_tokens": 9, "prompt_tokens": 10, "total_tokens": 19},