logger

Instance of a KamelosoLogger, providing timestamped and coloured logging.

The member functions to use are log, trace, info, warning, error, critical and fatal. It is not __gshared, so instantiate a thread-local KamelosoLogger if threading.

Having this here is unfortunate; ideally plugins should not use variables from other modules, but unsure of any way to fix this other than to have each plugin keep their own kameloso.common.logger pointer.