--------
* Removed 'class_'/'class' keyword parameter from LCDictBasic.add_formatter,
it's no longer added to formatter sub-sub-dicts:
* it's not used by dictConfig, and
* it was inserted even when creating a custom formatter
* it's (perhaps harmless but) misleading: that's not how a custom formatter
is specified
Docs and tests updated accordingly.
* Added examples custom_class_formatter.py, custom_callable_formatter.py,
and brief descriptions in Guide To Examples