EZP-22643: "Missing form token from Request " when creating an object
after clearing cache

https://jira.ez.no/browse/EZP-22643

This patch adds a `ezxFormToken::isEnabled()`, to be used in
https://github.com/ezsystems/ezpublish-kernel/pull/858
Merge pull request #963 from ezsystems/fix_EZP-22643_MissingFormToken

EZP-22643: "Missing form token from Request " when creating an object after clearing cache