Allow binding variables to loggers

This is to allow custom arguments to be logged with every message
returned by a logger.

Use-case: in centralized logging, I want to know which application
generated every message.
To be honest, I dunno. I currently don't override the binded arguments and I don't know if I ever will. Things like "late-binding" or bind-overriding come to mind but that might never happen.

Why would this not be a feature of the interface? Does MemoryLogger not need that? But, then, again I guess I don't really understand the purpose of MemoryLogger neither atm.