Don't import dev in project template settings

Developer settings were always imported whenever any portion of the
project template settings package itself was imported. Using production
settings would result in __init__.py importing the dev settings first,
*then* overriding those with the production settings.

This lead to somewhat counter-intuitive behaviour - dev settings that
weren't explicitly set again in production would tag along to prod.

To fix this, the project template settings package no longer imports
dev, and settings.dev is explicitly used in both manage.py and wsgi.py.

wagtail/project_template/manage.py

@@ -5,7 +5,7 @@ import os
 import sys
 
 if __name__ == "__main__":
-    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "{{ project_name }}.settings")
+    os.environ.setdefault("DJANGO_SETTINGS_MODULE", "{{ project_name }}.settings.dev")
 
     from django.core.management import execute_from_command_line
 

wagtail/project_template/project_name/settings/__init__.py

@@ -1 +0,0 @@
-from .dev import *

wagtail/project_template/project_name/wsgi.py

@@ -13,6 +13,6 @@ import os
 
 from django.core.wsgi import get_wsgi_application
 
-os.environ.setdefault("DJANGO_SETTINGS_MODULE", "{{ project_name }}.settings")
+os.environ.setdefault("DJANGO_SETTINGS_MODULE", "{{ project_name }}.settings.dev")
 
 application = get_wsgi_application()