Relate built-in user and custom user data

[Steven-Chan]

• auth_user and polls_user should be 1-to-1 related in db
• should not have two tabs in side menu
• should be able to edit the user in one single page, or two separate pages with link to each other in the form

[Steven-Chan]

Please help also update:

	Show all auth_user data in this page, including: username, email, permissions and groups, is_active, is_staff, is_superuser, date_joined and last_login.
	Edit all auth_user in this page, including: password, username, email, permissions and groups, is_active, is_staff, is_superuser, date_joined and last_login.

Try to include them as much as possible if not all. We need to demo keeping most functionality of the original django admin site with django-material, and figure out if anything requires customisation. For example, if change password requires a custom page, we can open a new issue to deal with that, now we can display a dummy custom page.