Logger class

[lacava]

implement simple logging class with user-controlled verbosity and option to direct to file.

resources:

• https://cppcodetips.wordpress.com/2014/01/02/a-simple-logger-class-in-c/
• https://github.com/google/glog
• https://github.com/gabime/spdlog
• https://github.com/SergiusTheBest/plog

[lacava]

This one looks like a winner: https://github.com/gabime/spdlog

• has a conda package as well: spdlog