GDPR: Include user data in WordPress export

WordPress 4.9.6 (due for release tomorrow, release candidates available) includes a new feature allowing export of all a user’s data. (This is necessary for sites that desire GDPR compliance, or just for anyone who thinks that allowing users to see what data you have on them is the right thing to do).

Currently, VFB does not hook in to include its data (specifically, the forms submitted by a particular user) in this export. So, the export is incomplete/misleading.

Here’s the patch used by another plugin to add this feature, showing the relevant WP hooks to use, and how to use them: https://github.com/AffiliateWP/AffiliateWP/pull/2666