Bump logging protocol version.
Logger is now manipulates with record entity instead of parameter packs.

Formatter objects are now accept log record object. This makes code a bit cleaner.
Ability to merge various properties into single collection.
Log record review.

 - drop path and lineno properties, because it seems to be noone needs it.
 - source field must be set explicitly.
Log record has been moved to the separate file.
Reduce dependencies.
Copyright headers added.