Add permalink update hook

[UTCGilligan]

First time the plugin is activated on a blog, new posts do not work: 404. However, the INITIAL Preview works, because it has the custom post type slug in the UL parameters. After a post is published, Preview no longer works.

This is due to WordPress Permalinks. Admin must SAVE Permalinks again to regenerate and register the new CPT slug.

• https://wordpress.stackexchange.com/questions/96988/is-there-an-action-for-when-permalinks-are-rebuilt