Update Newtonsoft.Json library

New version is 4.5.0.0 of assembly and version and 5.0.6.16206 of file version
Refactor name of CouchResponse and CouchWebResponse to restore consistency.

CouchResponse is now the counter-part of CouchRequest.
CouchResponseObject is a thin wrapper around the JObject returned from CouchDB. It also contain the StatusCode of the response.
Merge pull request #52 from teci/RefactorWebRequest

Refactor web request