fserv v0.20

+ http-proxy: added source code for proxy module and its default filters
+ http: separate access log
+ http: active connections are closed on server stop
- http: fixed segfault in some cases when there's an error in configuration
- http: fixed memory leak on error at a connection initialization
+ net.connect: all keep-alive connections are closed on server stop
- net.connect: fixed segfault on server stop
- net.connect: upstream server was mistakenly marked as 'down' after the connection to its first address had failed
* log: context log-level is now inherited
- log: unix: if a server was started as a daemon, there was invalid PID in logs
- core: stop signal wasn't sent to already started modules on error during server startup