1.1.5 -> 1.1.6
  * added reqdeny / reqallow rules
  * added HTTP 400 and 403 responses
  * chain regex in a list
  * reply 502 when no server is available
1.1.6 -> 1.1.7
  * implement global logging
  * have a single log function
  * add x-forwarded-for
  * log http requests on demand, and destination server name
1.1.7 -> 1.1.8
  * full HTTP log with destination server ID, req and resp time.
  * source address of outgoing connections
1.1.8 -> 1.1.9
  - handle parametrable HTTP health-checks replies
  - differentiate http headers and http uris
  - support environment variables in config file
  - support keep-alive

--- Notes about cookie usage ---

Cookie insertion is done at the end of server response.
Cookie matching is done after header replacement, but before
header deletion. This means that it's perfectly possible to
delete an inserted cookie once it has been matched, so that
the server never knows about it.

