Research on applying the new style to JH for registration and login pages

Background

We have to consider the language switch issue #923 (closed) before apply the new style to JH.

Screenshots

Login	login failed	forget password	sign up	trials	trials/new

How to apply

1. Apply new style to JH user auth flow by designer
2. implement the new design page into JH by frontend and backend engineers
3. add :zh translations for new items by engineers and technical writer
4. Enable this feature by deployment (this step may be at the first)