Prefer landing page url to url

[GlazerMann]

The other URL seems to not always be reliable. Just plain "url" seems to involve some post-processing on their part (which is not always right):
https://api.oadoi.org/v2/10.1671/0272-4634(2002)022[0058:ADATDF]2.0.CO;2?email=not@telling.com
This also seems to be more likely to point to the description page instead of the final pdf, which is probably better since most people just want that.
Also, it gives a url more often. See the test that is updated.

[codecov]

Codecov Report

Merging #512 into master will decrease coverage by 3.23%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master     #512      +/-   ##
============================================
- Coverage     75.73%   72.49%   -3.24%     
  Complexity     1433     1433              
============================================
  Files             9        9              
  Lines          2464     2465       +1     
============================================
- Hits           1866     1787      -79     
- Misses          598      678      +80

Impacted Files	Coverage Δ	Complexity Δ
Template.php	79.4% <100%> (-4.47%)	1281 <0> (ø)

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