This avoids instantiating dozens of loggers outside of debugging, but allows fine-grained control during debugging.

* Move old debugs to the new per-slot loggers
* Move old errors to a new module-level logger that always exists
* Add more debugs for better tracing what slots are doing

This should give flexible control. Logs from operator.py for a specific op (e.g. `lazyflow.op_debug.OpPixelClassification`) can be separately controlled from the individual module's logging for the same op (e.g. `ilastik.applets.pixelClassification.opPixelClassification`).

Some slots put unicode characters in the slot's meta dict. E.g. `OpPixelFeaturesPresmoothed.Output.meta.channel_names` will contain the sigma character. On Windows, the log file is encoded with cp1252 by default, which cannot handle such characters and raises UnicodeEncodeError.

Logging f"{slot}" is therefore not possible by default, as the slot's repr will contain the full meta dict along with the unicode chars.

So that default name is available during subclass.__init__ and slots instantiated can use it in their logger name.

This was always defaulting to "Wrapped Operator (base class)"