* admin users with is_master = 0, cannot see other admin users
(this includes system users) and brings the is_master flag
to the common behaviour
* ccareadmin, ccare users can now access te UI Admins page
as well as /api/admins but they are limited to see/manage
only themselves
* admin users cannot see system users (UI/API)
* reseller users cannot see system/admin users (UI/API)
* admin users cannot modify their own role and flags except for:
email, password, can_reset_password (UI/API)
* UI edit form now does not render fields that are not meant to be
modified by a user (exception: "login")
Change-Id: I82e1946437fd2ec4651abd24074470c695a40582