adds in basic geoblacklight schema validation and geoblacklight enhancment metadata

[mejackreed]

This pull request significantly improves support for GeoBlacklight-Schema. GeoBlacklight-Schema has moved away from being xml based to JSON based and this pull request modifies GeoCombine with this change in mind by doing the following.

• it creates a way to validate geoblacklight-schema json using the schema validation from https://github.com/geoblacklight/geoblacklight-schema/blob/master/geoblacklight-schema.json
• it modifies iso2geoBL.xsl to output json that is almost compliant geoblacklight-schema
• provides a way to create GeoCombine::Geoblacklight objects that do the following:
  • can be created with a valid JSON string of geoblacklight-schema
  • output valid json using #to_json
  • can take a fields argument as a Hash that merges with the original metadata
  • provides an #enhance_metadata method that does some enhancements, and translations on geoblacklight-schema metadata

[mejackreed]

Just wanted to cc other folks here for comment: @waynegraham @drh-stanford @eliotjordan @gravesm @kimdurante

[coveralls]

Coverage increased (+0.33%) to 97.89% when pulling a27ac41 on schema-validation into fdcf772 on master.

[mejackreed]

Also the enhance_metadata method should close #14

[coveralls]

Coverage increased (+0.33%) to 97.89% when pulling 7efc842 on schema-validation into fdcf772 on master.

[eliotjordan]

Apologies for the late reply. Just got back from 🍹 😎. This looks good. From geoblacklight/geoblacklight-schema#51 I see that idea is to move our geoblacklight.xml docs to geoblacklight.json docs. Is there a plan to remove xml support entirely at some point?

[mejackreed]

No worries @eliotjordan ... hope you had a good time. I think people will still be able to index xml docs, but the canonical format for geoblacklight-schema will be json. Validation in GeoCombine will happen using json schema validation.