Useful macro added.
Log formatting introduced.

* planning as another abstraction layer between logging handlers and log users.
Log level formatting added.
Drop source parameter to `emit` method

* also more verbose message on wrong formatting
File reorganization done.
Style.
Decomposition done over logging subproject.
Refactoring done.

* skeleton for msgpack formatter prepared
* basic formatter now have default time formatting method
* more style
Msgpack formatter has been implemented.
Log properties no longer storing in formatters.

* it's responsible of `log_t` objects
Package refactoring done.
Introducing json formatter.
Explicit copy of logger properties.

* also some in capsulation over formatter
Minor package restructuring.
Formatter is now part of api

* old logger hierarchy is actually handlers.
* log formatting functions moved into separate file.
* log property manipulation functions moved into separate file.
Config format concept added.
New logging configuration config parsing has been implemented.

* now to configure cocaine log you must specify both formatter and handler.
* next iterations will make formatter optional.
Injecting formatters into cocaine plugin system.

* new cocaine logging can now be fully configured through config files.
* log handlers no longer know about formatters.
* default format for string formatter has been provided.
Refactoring over json parsing for logging components.
Introducing socket handler for loggers.

* tcp & udp is only supported at this moment.