Bug 1080242 - Part 1: Extract clickable span helper.
Bug 1080242 - Part 2: Surface minimal messaging that Firefox Account is locked.

This just recognizes the locked state, and tells the user, "Account is
locked. _Resend unlock email_".  The "Resend unlock email" is underlined
and clickable.
Bug 1080242 - Part 3: Add FxAccountUnlockCodeResender.
Bug 1080242 - Part 4: Invoke unlock code resender.
Bug 1080242 - Surface "Account locked" state. r=rnewman