Adding acknowledgements

Ed contract credit and participants (just for this doc)
Setting up 8 April 2014 publication
Added ID to ack section
Fixing outputs of appendix sections
Links that went bad in the last month
Removed informative marker copied from WCAG
Additional acknowledgements

Previous contributors, commenters, etc. Probably missed some.
Merge remote-tracking branch 'origin/April-2014-republication'