Add xacml editor as dependency

This code  https://github.com/Islandora/islandora_paged_content/blob/0c45c9e523fbb7df99d2c1754730b52b8a13c83b/includes/manage_pages.inc#L782 assumes that Xacml editor is present, and the ingest process will fail if XACML editor is not present. 
Xacml editor should be listed as a dependency. It is true of 7.x-1.3 as well.