DownloadProvider: Properly open images

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: I3648b1c563acaa80b28a230bdb43ead3476cf3e7
DownloadProvider: Creates parent directories before creates file

Change-Id: I4b61c1aeb8054397fa2a2f162b068e683c7e9635
DownloadProvider: Remove download notification after preview

Removes download notification from the notification bar after
previewing it. There should be an additional check for download
shown in the notifications after completion to prevent from
situation when ContentObserver is unregistered and the onChange
is never called

Change-Id: I339c08152caf53342cf17e34c46e187fdad5a4c0
DownloadProvider: Clear notifications for Deleted items from Download list

Issue: Notifications for deleted items from the Download
list are not getting cleared and thus tapping on such
notifications causes crash (Illegal Argument Exception)

Fix: clear notifications for deleted items by adding them
in the stale list

Change-Id: I74e94ccca7ca79ec421d76023c5c894d9487e185