Fix/log must not be singleton

This MR remove the singleton behaviour with the recently introduced logging system. This fixes #127 (closed) and #128 (closed)

In addition, this MR make the issue

Also, The many changes are probably best reviewed per commits, the one being "removing the singleton" and the second one "move logger initialization into one class instead of shared among switcher.cpp and configuration.cpp".

In turn, class member formatting is using trailing "_" in the entire Switcher code base, this has been corrected for logger related members.