BAC-1231: change the way Cache-Control header is set

Remove X-Pass-Expires and rely on Cache-Control only
Typo
It should be "s-maxage"
BAC-1231: cleanup cache control related code
Remove varnishTTL / browserTTL related code
Merge branch 'dev' into bac-1231-cache-control-header

Conflicts:
	skins/oasis/modules/GlobalHeaderController.class.php
BAC-1231: use Cache-Control and X-Pass-Cache-Control headers
Update unit tests
Get rid of Expires response header

It's removed by Varnish anyway

Rely on Cache-Control instead
Merge pull request #2622 from Wikia/bac-1231-cache-control-header

BAC-1231: change the way Cache-Control header is set