Rename directionConnection to isDirect.
Reset client timeout count upon getting request.
Remove handleClientWriteError.
Do not take special handling on log with debug option.
Use debug log to print parent proxy.
Change default keep-alive value to 15s.
Collect client&server connection count, better debug message.

Some debug messages now contain "client: <remote addr>", we can group debug
message by client by grep and sorting on remote addr.
Script to group log by client.