Extend instance vars for more authority types

[mrmiguez]

RDA content: <genre authority="rdacontent">text</genre> RDA media: <form authority="rdamedia" type="RDA media terms">computer</form> RDA carrier: <form authority="rdacarrier" type="RDA carrier terms">online resource</form> COAR resource type: <genre authority="coar" authorityURI="http://purl.org/coar/resource_type" valueURI="http://purl.org/coar/resource_type/">bachelor thesis</genre>