Migrate defunct ImageJ User & Developer Conference content

The imagejconf.tudor.lu site is defunct now, and imagejdocu.list.lu does not have all the previous content. Let's migrate all the content from those conferences to imagej.net.

We can pull it out of the Wayback Machine:
- https://web.archive.org/web/20210420081811/https://imagejconf.tudor.lu/

The area of imagej.net where this content would go is:
- https://imagej.net/events/conferences
- https://imagej.net/events/conference-2006
- https://imagej.net/events/conference-2008
- https://imagej.net/events/conference-2010
- https://imagej.net/events/conference-2012

The 2008 content appears to [exist on imagejdocu](https://imagejdocu.list.lu/events/ijconf2008), although it should be manually inspected and compared against the content scraped from Wayback Machine before migrating.

Start with the Wayback Machine snapshot of imagejconf.tudor.lu and inspect the existing conference pages at imagej.net/events/conferences and the 2006, 2008, 2010, and 2012 URLs. Compare the 2008 page against imagejdocu.list.lu/events/ijconf2008, then migrate the missing conference content; done means all content from the archived conferences is represented on imagej.net.

Written by the indexing model from the issue text.