feature(client): Add a link to resend verification email for unverified users who change their password.

fixes #887
Merge pull request #975 from mozilla/issue-887-unverified-change-password

feature(client): Add a link to resend verification email for unverified users who change their password.
feature(client): Prevent users from seeing confirmation pages if they have not initiated the process.

* For /confirm, redirect to /signup
* For /confirm_reset_password, redirect to /reset_password

fixes #847