Move settings validation out of startup.py

This also creates a new app common_initialization in order to provide a
place to run initialization code common to both the LMS and CMS.

common/djangoapps/startup_configurations/validate_config.py

@@ -1,42 +0,0 @@
-"""
-Common Functions to Validate Configurations
-"""
-
-
-def validate_lms_config(settings):
-    """
-    Validates configurations for lms and raise ValueError if not valid
-    """
-    validate_common_config(settings)
-
-    # validate feature based configurations
-    validate_marketing_site_config(settings)
-
-
-def validate_cms_config(settings):
-    """
-    Validates configurations for lms and raise ValueError if not valid
-    """
-    validate_common_config(settings)
-
-    # validate feature based configurations
-    validate_marketing_site_config(settings)
-
-
-def validate_common_config(settings):
-    """
-    Validates configurations common for all apps
-    """
-    if not getattr(settings, 'LMS_ROOT_URL', None):
-        raise ValueError("'LMS_ROOT_URL' is not defined.")
-
-
-def validate_marketing_site_config(settings):
-    """
-    Validates 'marketing site' related configurations
-    """
-    if settings.FEATURES.get('ENABLE_MKTG_SITE'):
-        if not hasattr(settings, 'MKTG_URLS'):
-            raise ValueError("'ENABLE_MKTG_SITE' is True, but 'MKTG_URLS' is not defined.")
-        if not settings.MKTG_URLS.get('ROOT'):
-            raise ValueError("There is no 'ROOT' defined in 'MKTG_URLS'.")