Initial Commint
Summary: Created "Applications" application which lists all the installed applications in phabricator.
Test Plan: Navigated to localphabricatorinstall.com/applications and check whether it actually shows the list of all installed applications.
Reviewers: epriestley
Reviewed By: epriestley
CC: aran, Korvin
Maniphest Tasks: T2352
Differential Revision: https://secure.phabricator.com/D4548