GET /trackers/:id/tracker_reports

Task #6912. Part of story #6190.

Change-Id: If17ae2b2610af75d74c6396ec631c2422d284f98
GET /tracker_reports/:id

Task #6213. Part of story #6190

Change-Id: Ie145c99575efc626b62a0a1a22923c4693a1ddfe
GET /tracker_reports/:id/artifacts

Task #6214 and task #6215. Part of story #6190.

Change-Id: I6132b79542f883f14f57909210b75ccf9028d2b6
Merge remote-tracking branch 'gerrit/6190_get_tracker_reports' into stable

* gerrit/6190_get_tracker_reports:
  GET /tracker_reports/:id/artifacts
  GET /tracker_reports/:id
  GET /trackers/:id/tracker_reports

Conflicts:
	plugins/tracker/include/autoload.php

Change-Id: Id4544df829354fe6a9becb21f2f636e41f5b4e0c
This is Tuleap 6.10.99.35

Change-Id: I8f75f766a7df6b598476ae7757c40aed8a418ce1