Cache Directory "symbol" portion may contain characters ":" invalid for Windows

[FelixJongleur42]

As for now, cache folder could be something like caches/binanceusdm/BNB_USDT:USDT/.
This would not work under Windows, or under Linux where this directory is mounted to Windows host.
As an exercise, I will make a PR for this myself.

Code relevant for this is:

passivbot/src/candlestick_manager.py

Line 233 in 4f399b2

return symbol.replace("/", "_")

[FelixJongleur42]

I would plan to automatically detect Windows, and do an additional replacement of ":" to "_".
We could always do that regardless of the os, but that would "break" current setups under Linux.
To enforce this replacement even if under Linux, I would suggest an environment variable (good for Docker).
Enforcing is required, e.g., if running under Docker (Linux) while mounting the "caches" directory to Windows host.

[FelixJongleur42]

PR #548