Summary: Ref T7149. This flags allocated but incomplete files and doesn't explode when trying to download them. Files are marked complete when the last chunk is uploaded. I added a key on `<authorPHID, isPartial>` so we can show you a list of partially uploaded files and prompt you to resume them at some point down the road. Test Plan: Massaged debugging settings and uploaded README.md very slowly in 32b chunks. Saw the file lose its "Partial" flag when the last chunk finished. Reviewers: btrahan Reviewed By: btrahan Subscribers: joshuaspence, epriestley Maniphest Tasks: T7149 Differential Revision: https://secure.phabricator.com/D12063