Schema - Improve spatial_uri field

[mjanez]

Migrated from: mjanez/ckanext-scheming#10

Steps

GeoDCAT-AP Schema

• Add generic continents
  to: spatial_uri field.

• Add generic icon for non-spanish uris spatial_uris.html template.

• Add icons for countries.

DCAT-AP Schema

• Add generic continents
  and european countries
  to: spatial_uri field.

DCAT-AP Info

Property URI	Used for Class	Vocabulary URI	Vocabulary URI	Usage Note
dct:spatial	Catalogue, Dataset	EU Vocabularies Continents Named Authority List, EU Vocabularies Countries Named Authority List, EU Vocabularies Places Named Authority List, Geonames	http://publications.europa.eu/resource/authority/continent, http://publications.europa.eu/resource/authority/country, http://publications.europa.eu/resource/authority/place, http://sws.geonames.org/	The EU Vocabularies Name Authority Lists must be used for continents, countries and places that are in those lists; if a particular location is not in one of the mentioned Named Authority Lists, Geonames URIs must be used.

[mjanez]

Add icons for multiple countries based on EU Vocabs Country dac2a14