change spacingfunc to samplerfunc

binarycpython/tests/test_grid.py

binarycpython/utils/grid.py

binarycpython/utils/grid_options_defaults.py

binarycpython/utils/spacing_functions.py

examples/notebook_BHBH.ipynb

examples/notebook_HRD.ipynb

examples/notebook_api_functionality.ipynb

examples/notebook_common_envelope_evolution.ipynb

examples/notebook_custom_logging.ipynb

examples/notebook_extra_features.ipynb

examples/notebook_individual_systems.ipynb

examples/notebook_luminosity_function_binaries.ipynb

examples/notebook_luminosity_function_single.ipynb

examples/notebook_population.ipynb