style(Documentation/api): keep curl based examples consistent and correct

- fix curl examples where `http://` was missing.
- consistent passing HTTP method parameter (all examples now have -X ACTION at
 the end or the url, GET is implicit)
- quote url when it contains `&` , instead of escaping
Merge pull request #470 from ranjib/consistent_curl_examples

style(Documentation/api): keep curl based examples consistent and correct