frameworks: Status bar activity indicators for mobile data and wifi

![screenshot_2014-09-10-10-26-14](https://cloud.githubusercontent.com/assets/977360/4212871/2a0f1770-38a8-11e4-859a-ce0e89523d3e.png)

Google were nice enough to create xxhdpi drawables for us before removing them. Reverts "Remove signal/wifi activity indicator icon overlays." This reverts commit cc901c10bffdfb9c6b31e676dec36b47d949979. Included NetworkController.java modification from Iaaa556ffab3ed4be1da8016ed40d0a9c2efcde01.

Adding preference for arrows
PS14: Fixing errors
PS15: Turning arrows off done via actual removing drawables work, so when arrows are turned off,
they do not redraw statusbar anymore :-[
PS16: Commit Iaaa556ffab3ed4be1da8016ed40d0a9c2efcde01 merged to this one
PS17: Rebase to allow merge with latest source
Change-Id: I7aa85f7c8442c45d17e42cac7823dfe93e3f24c1
Conflicts:
	core/java/android/provider/Settings.java
	packages/SystemUI/res/layout/signal_cluster_view.xml
	packages/SystemUI/src/com/android/systemui/statusbar/SignalClusterView.java
	packages/SystemUI/src/com/android/systemui/statusbar/policy/NetworkController.java