Handle special rights status for parent works

[wulman16]

• If the value of a work's rights status is "Not Applicable," Lux will not render a link to the value's (non-existent) rightsstatement.org page. This behavior is specifically for parent works whose children have differing rights statuses.
• The ParentCurateGenericWork Solr document fixture is updated with this new rights status. However, an automated test is not provided because it would be too brittle to be useful.

[wulman16]