Author: David Mudrák
MDL-62309 tool_policy: Add api::get_agreement_optional() method
This method allows to quickly check if the given policy version is
marked as optional or compulsory. This will be needed in other places
such as permissions check.
http://git.moodle.org/gw?p=moodle.git;a=commit;h=faf4222edcb0baea646df932dbf400f0f539c54f
http://github.com/moodle/moodle/commit/faf4222edcb0baea646df932dbf400f0f539c54f
+ 3.6 en [cachedef_policy_optional,tool_policy]