Issue #923882 by mrfelton | steveparks: Fixed Install warning when Administer Users by Role is activated by an installation profile.

#256469: always disallow editing/deleting uid1 (except when edited by self); removed 'authenticated user' from permissions and checks, since it's implicit

ported to 6.x (#242792), cleaned up to follow coding standards (#319082), restricted deleting from admin/user/user page (#270852)