Open images with content://media/ instead of content://downloads/ URI.

This allows images to be shared directly after opening them with the
DownloadManager.

Change-Id: I65c79923b7aef4c1113e572030c9c7f750b73df0
Fix download notification click behaviour.

PendingIntent.getBroadcast() doesn't update the intent extras if not
explicitly given something to distinguish the intents. This caused the
notification on-click to do nothing on everything but the first
download.

Change-Id: Ie69459c8bd31922133d7d1d130b2835c84e6037a
JIRA:CYAN-756