[FEATURE] Set up a logging system across the project
We need to set up logging across the project in order to be able to debug future bugs easier for all users, as some unexpected exception may happen and be lost.

A new `api/logging.py` file should be created, which will either define logger creation options, or create a logger instance. If it requires some env variables, then logger is created inside settings

The logger formatting should be as follows:

`22-10-2020 17:56:00.05 | INFO | api.models.Invoice.create | started creating invoice`

The format may be changed, any suggestions welcome. So it's a date, log level, function that logs something, and the message itself

`logging.handlers.TimedRotatingFileHandler` should be used as a logging handler, by separating logs per day. Logs should be probably saved in `logs/` directory.

Merchants API should expose log files (only with `server_management` scope) via some API endpoint, and admin panel  should provide a way to view logs for server admins.

Each component should do logging when necessary, and sometimes when not too (by using loglevel `DEBUG`).

Daemon might have logs enabled too to be able to diagnose errors in daemon implementation or electrum itself. 

Also, all exceptions must be logged. Maybe a global exception handler can be installed, like `sys.exc_hook`, which will log the error and then raise it