Fix UI: bootstrap issues

* cardwall card actions margin
* a.btn text-color
* crossref icons
* cardwall searchbox
* Tracker FormElement Checkbox

Change-Id: I908423c470399f7187b6b91e6f13f27294ba696f
Merge commit 'refs/changes/72/1372/3' of http://gerrit.tuleap.net/tuleap into HEAD

* http://gerrit.tuleap.net/tuleap:
  Fix UI: bootstrap issues

Change-Id: Ie61206905ffab8c6b248f6d5583cd7e107fd3a98
This is Tuleap 6.6.99.16

Change-Id: I544401942ab684b1064cb095f45fb337298ec876