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.

cms/envs/common.py

@@ -925,6 +925,9 @@ INSTALLED_APPS = [
     'djcelery',
     'method_override',
 
+    # Common Initialization
+    'openedx.core.djangoapps.common_initialization.apps.CommonInitializationConfig',
+
     # Common views
     'openedx.core.djangoapps.common_views',
 

cms/startup.py

@@ -15,7 +15,6 @@ from openedx.core.lib.django_startup import autostartup
 settings.INSTALLED_APPS  # pylint: disable=pointless-statement
 
 from openedx.core.lib.xblock_utils import xblock_local_resource_url
-from startup_configurations.validate_config import validate_cms_config
 
 
 def run():
@@ -40,9 +39,6 @@ def run():
     xmodule.x_module.descriptor_global_handler_url = cms.lib.xblock.runtime.handler_url
     xmodule.x_module.descriptor_global_local_resource_url = xblock_local_resource_url
 
-    # validate configurations on startup
-    validate_cms_config(settings)
-
 
 def add_mimetypes():
     """