Added function to get a log level from a case-insensitive string
Update Levels.hpp
Update Levels.cpp
Changed to std::lower
Update Levels.cpp

used std::transform wrongly
Update Levels.hpp
removed vertical whitespaces in unit test
bracket after TEST declaration
Merge pull request #100 from ethz-asl/feature/sm_logging_level_from_string

Added function to get a log level from a case-insensitive string