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