trunk-tracking: update from r3736 to r3770

Updated global_only options to include the correct APACHE_CONFIG_OPTIONX directives.
Removed repeated tests for prioritize_critical_css basic functionality.
Added new tests, mostly downstream caching tests and related pagespeed.conf updates. Also added missing pagespeed.conf updates for downstream caching.
Added support for checking option scope.
Merge pull request #616 from pagespeed/jud-trunk-tracking

trunk-tracking: update from r3736 to r3770