Sessions now expire after a much shorter amount of time, requiring
clients to issue API requests for session extension. This is handled
behind the scenes as the user interacts with the page, but once session
expiration is imminent, a modal appears which informs the user of his
inactivity and presents him with the choice of loging out or preserving
his session.
Change-Id: I68008d45859c814a835d65d882ad5ad2199d618e
