Use PHUIPinboard UI for embedding Pholio Mocks

Summary: Changes the old dark embed to match the PinboardView. Retains ability to target individual files. Removes "carousel" of files (not super useful?)

Test Plan:
Tested embedding Mocks, with and without targeting specific files. Tested Pholio Pinboard, Macro Pinboard.

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Reviewers: epriestley

Reviewed By: epriestley

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9531