Bug [#43512327] Redirect to login on sign out

Added a polling mechanism in the staffplan-app file. It polls every 10
second to make sure that there is connectivity and that the credentials
are good on the server. The user gets redirected to the login page if
they're not. We might want to refine the error message or the conditions
leading to the redirect in the future (maybe use that for the other
"similar" feature too).
Merge branch 'master' into redirect_to_login_automatically_on_sign_out
tweaks
Merge pull request #86 from rescuedcode/redirect_to_login_automatically_on_sign_out

Redirect to login automatically on sign out