Add the http::>ha format code and make http::>h log virgin request headers

Add the http::>ha format code and make http::>h log virgin request headers

This patch:
 - Modify the existin "http::>h format code to log HTTP request headers
   before any adaptation and redirection
 - Add the new format code "http::>ha" which allow the user to log HTTP
   request header or header fields after adaptation and redirection.

This is a Measurement Factory project.