HeadsUp: Launch in floating window

Add some part of NotificationHelper
Credits to AOSPA team

Taken from:
https://github.com/lion0738/android_frameworks_base/commit/9e4b4b3bf10ccaee3ff64bb7b74f929210b85d69

Change-Id: I7001cebd69790b46b8dcfe9150c7ef104e5427a2
HeadsUp: option to launch in floating window [1/2]

Change-Id: Ia8ffb4088f5b48b222a77ef486ba8b14e193c26f