Fix sla #2847 and sla #907 Git and jenkins usage

Fixes:
- Git post push commit now pass token to the URL to build
- No longer enforce SSL verification of Jenkins server
- Now use proxy if any defined to communicate with jenkins server

Nota: make use of core Jenkins integration.

Change-Id: Ia26ca44b7d70b6bbf436a591d8472355796ec91b
Merge commit 'refs/changes/64/364/2' of http://gerrit.tuleap.net/tuleap into tuleap-stable-master

* http://gerrit.tuleap.net/tuleap:
  Fix sla #2847 and sla #907 Git and jenkins usage
Tuleap 5.12.99.31