Bug 1022748 - Part 1: Pass extras through setup activities.

This also passes the password button's show/hide state between create
and set up.
Bug 1022748 - Part 2: Use custom server URLs passed through extras in setup activities.
Bug 1022748 - Part 3: Pass through server details to update credentials activity.

This information can be extracted from the AndroidFxAccount object in
the activity, but feeding the information through extras keeps the
processing and display pipeline uniform across all setup activities.
Bug 1022748 - Part 4: Don't show Get Started activity when custom server URLs are passed.

The Get Started activity provides no feedback about custom URLs, and it
just gets in the way of power users, so skip it entirely.
Bug 1022749 - Part 1: Show custom server URLs in setup activities.
Bug 1022749 - Part 2: Show custom server URLs in status activity.