Data Citation content fixes

[danielskatz]

The bottom link on https://force11.org/info/joint-declaration-of-data-citation-principles-final/#endorsement-list to the actual endorsement list is broken. Some of the endorsers feel that it's important to still have this working

[mrchristian]

Apologies for delays:

Fixes on: Joint Declaration of Data Citation Principles

https://force11.org/info/joint-declaration-of-data-citation-principles-final/

• Endorsement list link repaired
• Glossary and Example links added back in
• Other links in connected pages also added back in

An archive copy of the pervious site should be available here for checking purposes https://dev-force-11.pantheonsite.io/datacitationprinciples

Some documents on the linked pages were iframe embeds. We will look to move the content onto the site so that related items can be maintained.

Additionally we will move the content to a more appropriate layout for an article, while keeping same URL.