Make swarm to write logs to cocaine

Implement swarm_logger_interface with cocaine::logger as backend
Merge pull request #19 from andrusha97/master

Add support of netlink in libipvs build script
IPVS IPv6 support.
More IPv6 stuff for the IPVS service.
Trying to bind VSes using all possible PFs.
Changelog update.
Adapt to Resolver updates in the Core.
Typo.
Got in line with the corresponding Core branch.
Logs are non-const in other plugins, so keep it.
Fixed invalid initialization of urlfetch

Invalid order of members initialization
Changelog update.
Fixed runtime dependency for urlfetch package
Fixed log level in swarm_logger
Changelog update
Sync with the Process Isolate.
Added "connections-limit" option to URLFetch

This options set the limit for active connections
Changelog update
Do not try to log ignored messages.
Merge branch 'master' of https://github.com/cocaine/cocaine-plugins