Since now SecuritySettings is a fragment, not an activity, reacting
to intents is not easier anymore. The new activity is transparent,
and it works just like a dialog. This change also refactor'ed
SecuritySettings by moving some preference construction into
security_settings_misc.xml.
Bug: 3120992
Bug: 2117436
Change-Id: I8bd3fc7faa2a31d100b8d67310f9266260cfc31d
Improve the look of the UI, and add the confirmation screen
for enabling an administrator. This uses the new framework APIs
to show its description and policies it will control.