Add a way to serve differents apps on differents subdomains

Only one instance of Django is used to serve all the domains.

To test locally, add a line in your /etc/hosts file with
    127.0.0.1	sub.localhost
and add the equivalent line in local_settings.py:
    MULTIHOSTS_URLCONF = {
        "sub.localhost": "app.urls",
    }
Add static folder to gitignore
Typo