Simple fixes for broken DOIs (and alternate URLs)

[jimallman]

This is a short-term fix for the problems outlined in #20.

When we want to show a link to a DOI (or other URL), the page will check to see if it's a complete URL or a fragment. If the DOI (or URL) starts with http: or https:, it will be linked as-is. Otherwise, we should assume it’s a “bare” DOI and turn it into a CrossRef URL for display.

Given that the group submitting data is both small and trusted, this might be sufficient.

[jimallman]

I've added a few more touches to accommodate the existing variety of DOIs in the system.

• Strip all whitespace (including spaces, tabs, line returns) from the DOI/URL
• Strip any doi: or DOI: prefix
• Sheck for leading http: or https:
  • IF found, return the current string
  • ELSE wrap it in a CrossRef URL