[propertylib] refactoring

ogstools/meshplotlib/core.py

ogstools/meshplotlib/plot_features.py

ogstools/propertylib/__init__.py

ogstools/propertylib/custom_colormaps.py

ogstools/propertylib/matrix.py

ogstools/propertylib/mesh_dependent.py

ogstools/propertylib/presets.py

ogstools/propertylib/property.py

ogstools/propertylib/tensor_math.py

ogstools/propertylib/utils.py

ogstools/propertylib/vector.py

ogstools/propertylib/vector2scalar.py

ogstools/studies/convergence/convergence.py

ogstools/studies/templates/convergence_study.py

tests/test_propertylib.py