Subclass FileDepotRedhatDropbox from FileDepotFtp

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Add support_case to FileDepot

https://bugzilla.redhat.com/show_bug.cgi?id=965889
Merge pull request #115 from brandondunne/subclass_file_depot_redhat_dropbox

Subclass FileDepotRedhatDropbox