Changes to the exports, fixes #285

- XML export was slow, replaced SimpleXML with a simple script that outputs XML for massive performance gains
- New option in bootstrap to allow the cached XML export to also include the attachments
- CSV caching slightly rearranged, it's much more memory efficient now
- Some fixes to relatedevent orgs being shown even if showorg is disabled
- Added a new site admin action to generate several 3k events for load testing (slow)