Convert "profile" image transforms to the new pathway

Summary:
Ref T7707. This ends up being sort of complicated: to support 100x100 images in T4406, we need to scale small images up so they look OK when we scale them back down with background-size in CSS.

The rest of it is mostly straightforward.

Test Plan:

• Did an OAuth handshake and saw a scaled-up, scaled-down profile picture that looked correct.
• Used Pholio, edited pholio, embedded pholio.
• Uploaded a bunch of small/weird/big images and regenerated all their transforms.
• Uploaded some text files into Pholio.
• Grepped for removed methods, etc.

Reviewers: chad, btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7707

Differential Revision: https://secure.phabricator.com/D12818