Merge pull request #83 from fedora-infra/fas3_pingou

Project wide: pep8 review and fix.
Drop the update_people method as commits need to happen elsewhere
Add a method to flush the db session in the register
Add the url where the application is deployed in the configuration file
Add some configuration keys for email notifications
Add a dedicated form to create new account on FAS
Add a token generator in the fas.utils module
Add email settings in prod

Signed-off-by: Pierre-Yves Chibon <pingou@pingoured.fr>
Use pyramid httpexceptions to throw a 404 exception if user is not found
Add logic to create new accounts on FAS
Add links in the home page to the page to create a new account
Add the fas.util.notify module used to send email notifications
Add method to retrieve a user based on its password_token
Add endpoint to confirm account creation with the token sent by email
Flash some information to the user when the account was created/activated
Display the flash messages differently if they are error or information messages
In case someone already has this username/email address say so and display the flashed messages
Store the user's password encrypted
Add a property to People to check if the account has been activated or not
Adjust the login method to block account that have not been activated