profiles: Make the floating action button more material-y

This makes the FAB look consistent with other fabs across the system,
it adds animated elevation, changes the icon color to white but mainly
fixes the size which was completly wrong.

Change-Id: Ib8b2d54869a6a10958c24bcc0fab1224fd07fadd

Conflicts:
	res/layout/profile_tabs.xml
	res/values/styles.xml
	res/xml/security_settings_app_slim.xml
	src/com/android/settings/profiles/ProfilesSettings.java