[log] logging system

[AgwaB]

This is no longer future work. In an asynchronous environment, logging system is required!!! we can't expect many scenario and debug easily.

For example, go-ethereum has 6-level-log option
Logging verbosity: 0=silent, 1=error, 2=warn, 3=info, 4=core, 5=debug, 6=detail (default: 3)

And parity can only log special actions
sync=debug,rpc=trace

Now we use iLogger which based on logrus. and iLogger has 6-level for log
Info, Warn, Debug, Error, Fatal, Panic

And i think we need to log each component(Especially ACS, RBC, BBA) like parity can only log rpc or sync!

Reference
https://www.datadoghq.com/blog/go-logging/#track-golang-logs-across-microservices
https://github.com/DE-labtory/iLogger
https://github.com/sirupsen/logrus
https://github.com/ethereum/go-ethereum/tree/master/log

#128
-> it maybe used only test

[AgwaB]

@AgwaB