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
