Customizable Low battery pop-up warning (1/2)

Change-Id: Iacd26b4b111f853853adeaf900c762313aa3e056
Bring back the status bar activity indicators for mobile data and wifi

Google were nice enough to create xxhdpi drawables for us before removing them.

Reverts "Remove signal/wifi activity indicator icon overlays."

This reverts commit fcc901c10bffdfb9c6b31e676dec36b47d949979.

Change-Id: I7aa85f7c8442c45d17e42cac7823dfe93e3f24c1
Option to enable Notification Light when screen is on (1/2)... also Keep on notification LED while dreaming.
Add network usage stats to status bar (1/2)
PS2:
Get the time delta between updates and use that to show
average bytes per second.

Change-Id: I63771220333a32063f675e6fc38c9aadb6de4274

Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/res/layout/status_bar.xml
	packages/SystemUI/res/values/dimens.xml
	packages/SystemUI/res/values/styles.xml

Conflicts:
	core/java/android/provider/Settings.java
NetStats: Don't update stats when screen is off

Also moved registering of broadcast receiver and settings
observer to onAttachedToWindow() and unregistering to
onDetachedFromWindow() to avoid these being leaked.

Change-Id: Ia131a0db65c4c762b7f28493e812f9fb21358a27
Network stats: Hide if there's no traffic (1/2)