Trusting raw INSTALLED_APPS because early settings validation cannot succeed with a partial schema.
load_module('django.conf.global_settings') and Django1_5_5ConfigurationSchema have the same keys.
load_module('django.conf.global_settings') and Django1_6_2ConfigurationSchema have the same keys.
Reviewed README and INSTALL.
Introduced configuration schema for django-nose.
Replaced auto-discovery of local schemas by settings.CONFIT_SCHEMAS: fixes nasty circular imports.