Fix security issue on snippet service

SQL injection: add_snippet_to_package.php, addversion.php, delete.php,
detail.php, download.php, package.php, submit.php

XSS: add_snippet_to_package.php, addversion.php, detail.php

CSRF: add_snippet_to_package.php, addversion.php, package.php,
snippet_utils.php, submit.php

Change-Id: If66d31a915e155ff05251d4261e07078a5623424
Merge commit 'refs/changes/10/1710/2' of http://gerrit.tuleap.net/tuleap into HEAD

* http://gerrit.tuleap.net/tuleap:
  Fix security issue on snippet service

Change-Id: Ieda532348651477a39b83df5f4255a7d5496a95e
This is Tuleap 6.9.99.28

Change-Id: I3789ba8958abaf21bd9a9685a61f1e29a1c9346c