Fixed HTTP_CLIENT_RESPONSE when dealing with redirection
   before it was storing some header in the body.
   now we added redirections: ..  which is a list of redirection informations:
     - status line
     - header
     - and eventual redirection body (but at least by default, libcurl does not cache body)

Enhanced the http_client library to be able to write directly the downloaded data into a file (or as convenient thanks to agent).
added header helper feature in the context interface

added HTTP_CLIENT_SESSION.custom (...)
to support any kind of request methods
WSF_RESPONSE.put_header_text should use put_raw_header_data (and not append)
send the file date  for download file response.
Merge pull request #54 from colin-adams/master

Handle Precondition Failed for If-Match: * when no handler exists for the resource