Reworked transparent layer
When a halo'ed window is opened, the transparent layer will be always visible. It will manage the background dim.
This fixes some apps dimming its sandboxed processes (like chrome).

LayerActivity manages its own lifecycle. When it's focused after paused it finishes itself.

System processes (identified by "android" pkg in SystemUI and system uid in Activity) don't use the layer and still use their own background. This
has been kept this way to not interfere with their activity.
[1/2] Add triggers to change profile based on AP

Add data structure mWifiTriggers to store triggers per profile.
Add network change listener to switch to profile

Change-Id: I97e360d7783d3b0e2bbd70fe7a9a866d8c0fa7cd
LayerActivity: Corrected lifecycle
Should contemplate the case that the activity gets stopped
Fix little derp causing visual bug

To reproduce, disable halo, and press "clear all notifications" button

Change-Id: Ice7ab62229e27db53ef51fd5df55dbcd0a86358b