[logging] meta-logging macros for improved logging speed
[logging] meta-logging macros for improved logging speed

The easylogging++ logging macros are now wrapped in `ML_*` macros to
overcome unnecessary string conversion calls in runs and builds with
logging disabled.

This is based on work by @f-koehler.

Signed-off-by: Torbjörn Klatt <874eb11690ea5d8427c1f32853e3244a26aae295@fz-juelich.de>

memmett/PFASST,memmett/PFASST