Add a startup page for Nuxeo Drive web authentication

See details in NXDRIVE-211.
Basically let's add a JSP in nuxeo-drive-jsf that:

• Is guarded by the NuxeoAuthenticationFilter => contribute an URL mapping to web#STD-AUTH-FILTER.
• Is defined as a start URL => contribute a startURLPattern to the startURL extension point.

The page simply generates a token for the authenticated user and includes some JS code to provide this token to Nuxeo Drive.
This JS code uses the PyQt JS/Python binding so it necessarily depends on JS modules from the client.