Deprecate 'maniphest.enabled' and 'phriction.enabled'

Summary:
Also join concepts of installed and enabled applications.
Also respect uninstalled Maniphest where disabled Maniphest was checked.

Test Plan:
Visited T1, D1.
Uninstalled Maniphest then visited T1, D1.
Disabled Maniphest then visited T1.
Visited /config/edit/maniphest.enabled/.

Reviewers: epriestley, Afaque_Hussain, edward

Reviewed By: epriestley

CC: aran, Korvin

Differential Revision: https://secure.phabricator.com/D5602