Update couchdb to 1.5.0.

Changes since 1.4.0:
- COUCHDB-1781: The official documentation has been overhauled.
- New administration UI, included as an experimental preview.
- COUCHDB-1888: Fixed an issue where admin users would be restricted
  by the public_fields feature.
- Fixed an issue with the JavaScript CLI test runner.
- COUCHDB-1867: An experimental plugin feature has been added.
- COUCHDB-1894: An experimental Node.js-based query server runtime added.
- COUCHDB-1901: Better retry mechanism for transferring attachments during
  replication.