Add editors, translators and licensors fields to documents and binders
Merge pull request #75 from Connexions/add-other-user-fields

Add editors, translators and licensors fields to documents and binders
allow filtering user-content list by metadata fields, such as state or media_type
filter kwargs for user content; implement negation of match terms for storage doxument fetch
tests for user_content filters
keep js api camelCase, not_underscore