mailman.configuration -> mailman.config.config
mailman.initialize -> mailma.core.initialize
mailman.loginit -> mailman.core.logging (yay future absolute imports!)

Convert all configurations to lazr.config, though some legacy still remains,
and I haven't been able to remove Defaults.py yet.  Added as_boolean() and
as_log_level() helpers for explicit type conversion.  Added a schema.cfg.