New organisation of settings files

We reproduce what has been done here:
https://github.com/dissemin/dissemin

The following files can be found under `cof/settings/`
- `common.py`: the settings that are shared by all the environments we
  have + the secrets (see below).
- `dev.py`: the settings used by the vagrant VM for local development.
- `prod.py`: the production settings (for both www.cof.ens.fr and
  dev.cof.ens.fr)

There is also a notion of "secrets". Some settings like the `SECRET_KEY`
or the database's credentials are loaded from an untracked files called
`secret.py` in the same directory. This secrets are loaded by the common
settings file.

cof/settings/dev.py

@@ -0,0 +1,52 @@
+"""
+Django development settings for the cof project.
+The settings that are not listed here are imported from .common
+"""
+
+import os
+
+from .common import *
+
+
+EMAIL_BACKEND = 'django.core.mail.backends.console.EmailBackend'
+
+DEBUG = True
+
+TEMPLATES[0]["OPTIONS"]["context_processors"] += [
+    'django.template.context_processors.debug'
+]
+
+
+# ---
+# Apache static/media config
+# ---
+
+STATIC_URL = '/static/'
+STATIC_ROOT = '/var/www/static/'
+
+MEDIA_ROOT = os.path.join(BASE_DIR, 'media/')
+MEDIA_URL = '/media/'
+
+
+# ---
+# Debug tool bar
+# ---
+
+def show_toolbar(request):
+    """
+    On ne veut pas la vérification de INTERNAL_IPS faite par la debug-toolbar
+    car cela interfère avec l'utilisation de Vagrant. En effet, l'adresse de la
+    machine physique n'est pas forcément connue, et peut difficilement être
+    mise dans les INTERNAL_IPS.
+    """
+    if not DEBUG:
+        return False
+    if request.is_ajax():
+        return False
+    return True
+
+INSTALLED_APPS += ["debug_toolbar"]
+MIDDLEWARE_CLASSES += ["debug_toolbar.middleware.DebugToolbarMiddleware"]
+DEBUG_TOOLBAR_CONFIG = {
+    'SHOW_TOOLBAR_CALLBACK': show_toolbar,
+}