Add ``get_setting`` template tag.

The template tag is available in the ``core_settings`` module
and has been added as an accessory to read the app settings
from the templates.

This is in order to avoid to modify an existing view only
to add a setting in the template context.

e.g. Change password view.

Usage:

    {% load core_settings %}
    {% get_setting 'SITE_URL' %}
Add alias to run a simple SMTP server.

Usage:

    $ run_smtp
Add account management section.

The users should be able to create and manage access
to the account. The flow is as follow:

- User enters email and password.
- User receives email with activation URL.
- User activates the account by following the link.

The key sent expires in the 7 days.

There are more views for confirmation of the success or
failure of an action.

Management views included:
- Reset password.
- Login.
- Logout.