Install and configure shoal-client

Use yumrepo functionality to add shoal repository.  Install shoal-client
and the python-simplejson dependency.  Set cron job to run shoal client
every 30 minutes.

TODO: Once shoal-client dev branch is committed to yum repository remove
python-simplejson dependence.

Changes:
	modified:   shoal/manifests/init.pp
Install EGI Trustanchors

Install the trustanchors of the european grid initiative.  Required to
authenticate condor hosts.

Changes:
	modified:   gce_node/manifests/grid_setup.pp