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

@kparlante - can you see if this is a bit closer to what you were looking for?

@nchapman or @zaach - could one of you do a pass over this as well?

Add:
* signin.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.complete - users who complete the signup flow of any type.
* 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.

Hook up the debounce code to the password reset.

issue #1559
fixes #1147
Should this be `contex` or `context`?

I also see a reference to `contex` on [L337](https://github.com/mozilla/fxa-content-server/pull/1745/files#diff-a751175eb826ca71a4a1fbb4b30f3364R337), or actually 4 references if you search for `contex:` on [/app/tests/spec/views/sign_up.js:335](https://github.com/mozilla/fxa-content-server/blob/master/app/tests/spec/views/sign_up.js#L335)