Links for unit descriptions

[zdefne-usgs]

Links for unit descriptions do not work properly. Used a combination of following links t o fix.
8 occurrences of:
https://www.unidata.ucar.edu/software/udunits/udunits-2.2.25/udunits/udunits2-base.xml
16 occurrences of:
https://www.unidata.ucar.edu/software/udunits/udunits-current/udunits/udunits2-common.xml
3 occurrences of:
https://www.unidata.ucar.edu/software/udunits/udunits-2.2.25/udunits/udunits2-derived.xml
1 occurrence of:
https://www.unidata.ucar.edu/software/udunits/udunits-2.2.25/udunits/udunits2-accepted.xml
11 occurrences of:
http://www.xml-cml.org/unit/si/
15 occurrences of:
http://www.xml-cml.org/unit/nonSi/

However, rubric does not like the links that do not refer to an xml file.

[zdefne-usgs]

updated the links to xml files at https://github.com/Unidata/UDUNITS-2 instead of https://www.unidata.ucar.edu/software/udunits/.

Rubric complains about links to ww.xml-cml.org because they are not links to parts of xml files but to webpages.

[zdefne-usgs]

Reopening this issue because it is a constant pain. There is no representation for some of the units. How to handle them in the metadata? For example for velocity it can be something like this (but looks like hasn't been implemented yet):

<gmd:units xlink:href="https://raw.githubusercontent.com/Unidata/UDUNITS-2/master/lib/udunits2-common.xml#meter_second-1"/>

Posted on following discussions:

• How to handle units for velocity?
  Units for velocity? Unidata/UDUNITS-2#84

• How to automatically create meaningful links for units?
  Remove reference to fake URL for units vocabulary. Unidata/threddsIso#14

[rmallen86]

Units of some fields show up as "inapplicable". It doesn't seem to be the "main" fields, but still - there should be some units right?