Deal with unsupported database versions more gracefully
Deal with unsupported database versions more gracefully

Instead of crashing with a function_clause error, allow the updater to throw
the error '{database_disk_version_error, "Incorrect disk header version"}'
when opening more recent, unsupported, database files.
This is part of COUCHDB-1081.



git-svn-id: c1f8a8ec0b3bb2e99ab3413722f81f687760e79c@1079966 13f79535-47bb-0310-9956-ffa450edef68

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