Provide a purchase detail view in Phortune

Summary: Ref T2787. This provides a purchase detail screen (which has nothing useful on it yet) and converts a bunch of PHIDs into slightly more useful links.

Test Plan: Browsed around my account.

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T2787

Differential Revision: https://secure.phabricator.com/D10284