Remove the double-swipe to access quick settings on phones.

On the plus side, the settings button is back!

Now that we have two buttons on the right-hand side it's
more important than ever that the notification panel header
not allow errant taps to go all the way back to the
notification panel, where they will drag/close it.

Bug: 7319756 // remove double-swipe
Bug: 7217201 // finally make the notification header black
Change-Id: I8b2d6c7a7cfaaed2bfbcd61fb45db9f234cb002d