Some refactoring of DMUser & DMUserMultiBehavior

Do the log from log_user_stat.hpp in DMUser rather than in DMUserMultiBehavior
test the log for DMUser tests -> see issue #25
add class DMUserDegradTemp / rename DMUserDegrad -> DMUserDegradSpatial + make DMUserMultiBehavior inherit from DMUserDegradTemp
same for class SeeULater
fill in the file src/users/user_description_file_template.json for documentation

Edited Oct 30, 2023 by Ghost User