DownloadProvider: Transfer speeds in notification

Change-Id: Ic7efcdfe7a329946f3b63c331064ac2f16faafeb
DownloadProvider: Normal notification for singles

This builds upon the previous DownloadNotifier, but changes
the notification style when downloading single files by
removing the big view.

Change-Id: I06d2b555bb51613661ccb50df3b7bc59439b2252
DownloadProvider: Standardize notifications

Standardize play store and browser download notifications
Image: http://i.imgur.com/w3VaRUK.png

Change-Id: Ibadcca3725b4adb330a5670414ac8f89790448b8