feat(metrics): Add metrics for signup, preverified signup, signin, hide the resend button.

Add:
* login.complete - for a user who signs in successfully.
* signup.preverified - for users who attempt to sign up with a preVerifyToken
* signup.preverified.complete - users who successfully sign up with a preVerifyToken
* signup.success - users who successfully initiate a signup.
* confirm_reset_password.resend - users who attempt to resend the password reset email.
* confirm_reset_password.too_many_attempts - when we hide the "Resend" button for password reset users who have tried too many attempts.

Also:
* Hook up the debounce code to the password reset.
* Add a base.js->logScreenEvent that logs an event using the screen name as the prefix.

issue #1559
fixes #1147