Multithreading Suppot For CCXT Newtwok Request

[JaCoderX]

Followed by the discussion in this post, I believe that there are a few design changes the backtrader-ccxt bridge need to take place.

At the current design, live requests are made over the network on the main thread, via the strategies and backtrader internals. That leave the software vulnerable to Hangs of the main thread.

As suggested in the post some/all request need to be managed on threads that keep updating values or do some other work in a way that doesn't delay the excursion of the main thread.

This is a vital refactor to make it possible to really use this project on production