R1:2db912e859e8

Add change password settings panel

Summary:
In password-based auth environments, there is now a user settings
panel to allow them to change their password.

Test Plan:
Click settings, choose password from the left:
* enter current password, new password (twice), log out, and log in with
new password
* enter current password, non-matching passwords, and get error
* enter invalid old password, and get error
* use firebug to change csrf token and verify that it does not save with
and invalid token…