Adding Phriction 'Document Index' link to the crumbs actions

Summary:
removed references to doc index from document controller / content display / whatever name it currently has

Refs T2686

Test Plan: saw it - touched it - tested it

Reviewers: epriestley, chad

Reviewed By: chad

CC: aran, Korvin

Maniphest Tasks: T2686

Differential Revision: https://secure.phabricator.com/D5342

Conflicts:

src/applications/phriction/controller/PhrictionDocumentController.php