Refactor connection tags

[kuznetsss]

Summary

Currently connection tags (file Taggable.hpp) are written in very OOP style with a lot of classes to follow OOP practices. It could be simplified. Also probably taggable could be a wrapper above log class doing logging with tag. Such design would guaranty that we didn't forget to put a tag somewhere.

[kuznetsss]

Current tags implementation may have an undefined behaviour if parent tag lives less than a child one. I'm adding bug label here. And also removing milestone to reconsider the urgency of this issue.