updates json schema to allow optional null values on non-required fields
Update single_entry.json
Update index.md
changing case of 'data'
updates to json schema
Separating references to labels and field names to avoid confusion

Also attempts to be more accurate in usage of labels for POD and DCAT
Updates references to different schemas and abbreviations
Merge pull request #271 from project-open-data/addresing-issue-94

Adds LIBRE tool originally offered in Issue #94
Merge pull request #269 from project-open-data/updating-the-json-schema-2

Update single_entry.json
Merge pull request #275 from philipashlock/update-schema-fieldname-labels

Closes #154 and updates #77 - Separates out confusing field name labels
Correcting mappings between POD schema and CKAN
Correcting mappings between POD schema and DCAT
accessLevelComment -> accessLevel

A small typo from the last update.
Merge pull request #280 from project-open-data/fixes-typo-on-schema-page

accessLevelComment -> accessLevel
Merge pull request #278 from philipashlock/update-schema-mappings

Update schema mappings