Return ok:true on _bulk_doc update

The tests are separated and are quite funky. The main
reason why I also submit them is to get some 
opinions and maybe a discussion  about 
integration-tests for `couchdb-chttpd` running.

- I could imagine something based on Erlang to test 
chttpd which has better quality than my code.

- Another solution would be something JS/node based,
I am more used to that and faster in writing JS, but it
may not apply to everyone

- Use a complete different language / solution to test

---

Return `ok: true` on a successful _bulk_doc update like in
CouchDB 1.6.

Example success message on 2.0:
```
[{"id":"Brocket","rev":"6-b6fa9e703c3eb92aa9c3a49cedf1e8c2"}]
```

Example error message on 2.0:
```
[{"id":"Blaggie-System","error":"conflict",
  "reason":"Document update conflict."}]
```

Finally closes COUCHDB-2462
clash with buitlin functions? yes, it have a place, but don't see why coping module helps to solve that...