Implement Role Switcher

[DaiYuzeng]

Due to the unimplemented logic of Login, We need to add a Role Switcher Component on the right corner of Header.

It should be able to:

• [x] Clickable to switch different roles(Shareholder, Gold, Silver)
• [x] Use global state to manage current role
• [x] Particular components like the form of "Book Tee Time/Request Standing Tee Time" should be affected by the current role
• [x] Home page needs to display "Welcome, {Role} {MemberName}"