Pass instance through file transform URIs

Summary:
This makes thumbnail URIs work on instanced, CDN'd installs like Phacility cluster instances.

Some of these transforms can proabably be removed, but the underlying code to generate the transform should be cleaned up too and we have some other tasks filed elsewhere about this anyway.

Test Plan: CDN'd local install now loads thumbnails properly.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Differential Revision: https://secure.phabricator.com/D11719