[WIP] HeadsUp: optional whitelist mode (2/2)

The frameworks half of this is happy without this for now.
TODO: make the "whitelist" (known as the blacklist) reload properly when you open headsup settings after checking the whitelist mode checkbox?
      or maybe just try take a look at this tomorrow and facepalm about whatever stupid problem is impeding functionality

Flips the per-app HeadsUp logic

Change-Id: Id9f830b488d9cfefe1851a4ed6bd939b7f136852
Automatic translation import

Change-Id: Icb77a2c1f07d2e54f64928f32f0b16482772fe47