Support for binary responses in ClientDriverResponse

Modified ClientDriverResponse to use a byte array for internal representation of content.

Created constructor to allow the creation of a ClientDriverResponse taking an InputStream as an argument. The default Content-Type of a ClientDriverResponse created using this constructor will be "application/octet-stream".

Increased test coverage on ClientDriverResponse.

Note:
The character set specified in the Content-Type header now no longer defaults to ISO-8859-1. Character sets will now have to be set manually. This is due to moving from HttpServletResponse.getWriter() to HttpServletResponse.getOutputStream() to enable writing of binary content.