Added code to retain existing URL parameters across different view types

There were a couple of routing errors and code crashes due to absence
of certain URL parameters when the view type was switched from grid to
list or tile, or when the list was sorted.
This has been fixed in the current commit.
Other than this, a missing route for 'download_data' was added as well.

https://bugzilla.redhat.com/show_bug.cgi?id=1130223
Merge pull request #552 from AparnaKarve/bz1130223_fix_url_and_add_missing_routes

Retain existing URL parameters across different view types