Add Download Speeds in notification

This commit adds the ability to show the current total download speed

Screenshots: http://goo.gl/M3eRNR

ps7 : remove download site, and make speed to bit/sec
ps8 : make speed to byte/sec and cleanup
ps9 : revert to B/sec
ps10: fix some formatting issues
ps13: rebased

Conflicts:
	res/values/cm_strings.xml
	src/com/android/providers/downloads/DownloadNotifier.java

Change-Id: I801dbe61c7ee59d0c1d14d5851ad6dc3a7678499