Added a method streaming_enabled, to know if a model has streaming enabled
Added an option for both Poe and OpenAI to generate text with streaming in settings
Moved the code relative to text streaming in classes
LLM Handlers that now implement streaming, have to implement a send_message_stream, method, that also receives a function on_update, that is ran at every message update, with first argument the message text generated till now, and some extra_arguments that are passed when send_message_stream is called
Addresses #34
streaming_enabled, to know if a model has streaming enabledsend_message_stream, method, that also receives a function on_update, that is ran at every message update, with first argument the message text generated till now, and some extra_arguments that are passed when send_message_stream is called