Merge branch 'doc/settings' into 'master'

Clarify some things about settings with some comments

See merge request !315

website/thaliawebsite/settings/__init__.py

+"""
+Settings module
+
+This file controls what settings are loaded.
+
+Using environment variables you can control the loading of various
+overrides.
+"""
+
 # flake8: noqa
 import os
+
+# Load base settings
 from .settings import *
+
+# Attempt to load local overrides
 try:
     from .localsettings import *
 except ImportError:
     pass
 
-if os.environ.get('DJANGO_PRODUCTION'):
+# Load production settings if DJANGO_PRODUCTION is set
+if os.environ.get('DJANGO_PRODUCTION'):  # pragma: nocover
     from .production import *
-if os.environ.get('GITLAB_CI'):
+
+# Load testing settings if GITLAB_CI is set
+if os.environ.get('GITLAB_CI'):  # pragma: nocover
     from .testing import *

website/thaliawebsite/settings/production.py

 """
-Django settings for thaliawebsite project.
+Django production settings for thaliawebsite project.
 
-Docker version
+Many of these settings override settings from settings.py.
+
+This file is loaded by __init__.py if the environment variable
+`DJANGO_PRODUCTION` is set.
 
 See https://docs.djangoproject.com/en/dev/howto/deployment/checklist/
 """

website/thaliawebsite/settings/settings.py

 """
 Django settings for thaliawebsite project.
 
-Generated by 'django-admin startproject' using Django 1.10b1.
+This file is loaded by __init__.py.
+
+Its settings may be overridden by files loaded after it.
 
 For more information on this file, see
 https://docs.djangoproject.com/en/dev/topics/settings/

website/thaliawebsite/settings/testing.py

+"""
+Settings for CI testing
+
+This file is loaded by __init__.py if GITLAB_CI is set in the environment
+"""
+
 DATABASES = {
     'default': {
         'ENGINE': 'django.db.backends.postgresql',