Support of redirection to the previous page after authentication

[laurentj]

When the user tries to go to a page A although he is not authenticated, he is redirected to the login page. After the authentication process, he should be redirected to the page A instead to the home page.

To avoid security issues, if he is redirected to an external web site:

• the redirection should be allowed by a configuration flag
• the domaine name should be into a white list, to be authorized to go to the web site