Disable Immersive Messages [2/2]

Ported to L by Deadman96385

Based off Xposed module by GermainZ

https://github.com/GermainZ/ImmersiveModeDontPanic

Change-Id: I4835cac08a9e525ec15aa4d1ee84329970ec6a72

Conflicts:
	policy/src/com/android/internal/policy/impl/ImmersiveModeConfirmation.java
Revert "Revert "wlan: Provide runtime option to enable or disable rssi threshold (base)""

This reverts commit 0c2ddda1e6992e71350deea55c2350adff46b399.