tasks #6672: Hide html diffs by default, display them on click on "show" button

Change-Id: I21bcc84c9d36f82f715722a4f04530b705603539
Merge commit 'refs/changes/84/2284/5' of ssh://gerrit.tuleap.net:29418/tuleap into HEAD

* ssh://gerrit.tuleap.net:29418/tuleap:
  tasks #6672: Hide html diffs by default, display them on click on "show" button

Change-Id: Ie808c5f1a2d7996a589cd14e509bb72a483aa97d
This is Tuleap 6.12.99.64

Change-Id: I0b718f921b9e509f955a6c20c8f63a106d6039da