Add default.yaml

[mdoering]

Allow an optional default.yaml file to provide default values for all terms. This needs to be a map of entities with a list of terms. If the term is defined in the actual data default values will only apply in case the value is null. E.g. it can be used to have a default extinct value, but override it for exceptional records.

E.g to declare the same kingdom, nomenklatural code or vernacular name language without the need to add a column to data files with the same value all over. Similar to meta.xml in dwca

[mdoering]

Example default.yaml file:

Name:
  code: zoological
Taxon:
  extinct: false
  environment: marine

[mdoering]

@dhobern @gdower @camiplata @thomasstjerne I have implemented this proposal already in ChecklistBank. Might be useful for some of your ColDP archives.