rename django_shell.sh to django_manage.sh and pass arguments

Instead of a dedicated script to call the shell, this will call
manage.py and pass all following arguments to it.
So you can call `./scripts/django_manages.sh shell` or
`./scripts/django_manage.sh makemigrations abcapp` followed
by `./scripts/django_manage.sh migrate`.
Chmod phpBB files/dirs recursively to fix store/read phpBB settings

If the files below forum/cache are not writeable phpBB cannot change
data_global.php (and all other values). This leads to problems like
having a stale cookie_name in the cached config data and phpBB will use
that to generate the cookie.