Only allow strings in user doc "roles" array
Only allow strings in user doc "roles" array

We validate that _security documents only contain strings but we have
not done the same for the roles field in user docs. This is a breaking
change as users may have been inserting other things (notably,
objects) in this field.

COUCHDB-1675

alanning/couchdb-couch,apache/couchdb-couch,fkaempfer/couchdb,ngpestelos/couchdb-couch,cloudant/couchdb-couch,KlausTrainer/couchdb-couch,KlausTrainer/couchdb-couch,apache/couchdb-couch,smithsz/couchdb-couch,alanning/couchdb-couch,ngpestelos/couchdb-couch,smithsz/couchdb-couch,smithsz/couchdb-couch,alanning/couchdb-couch,apache/couchdb-couch,fkaempfer/couchdb,fkaempfer/couchdb,cloudant/couchdb-couch,cloudant/couchdb-couch,KlausTrainer/couchdb-couch,ngpestelos/couchdb-couch,fkaempfer/couchdb,fkaempfer/couchdb,fkaempfer/couchdb