MEDIUM: http: add a new "http-response" ruleset

Some actions were clearly missing to process response headers. This
patch adds a new "http-response" ruleset which provides the following
actions :
  - allow : stop evaluating http-response rules
  - deny : stop and reject the response with a 502
  - add-header : add a header in log-format mode
  - set-header : set a header in log-format mode
7 files changed