Better UI feedback when registration failed

[dpocock]

Currently, if registration fails due to a bad password (401 or 407 error codes) the UI shows "SIP Registration failure" but it also shows the boxes for users to try and dial or chat.

Maybe the other functionality should be disabled when registration is in this state?

Maybe the error should give a link to log in again? Currently, the user can go back to the login form by clicking the logout link (provided in the fix for #23) but it would be nice to make it more obvious that the user should try to login again.