Merge branch 'mr_fourth_order_cumulants' into 'master'

conftest.py

doc/sphinx/lbmpy.bib

lbmpy/creationfunctions.py

lbmpy/db.py

lbmpy/methods/abstractlbmethod.py

lbmpy/methods/cumulantbased/__init__.py

lbmpy/methods/cumulantbased/cumulantbasedmethod.py

lbmpy/methods/cumulantbased/fourth_order_correction.py

lbmpy/methods/momentbased/entropic.py

lbmpy/methods/momentbased/momentbasedmethod.py

lbmpy/scenarios.py

lbmpy_tests/cumulantmethod/test_flow_around_sphere.py

lbmpy_tests/full_scenarios/shear_wave/scenario_shear_wave.py

lbmpy_tests/test_force.py

lbmpy_tests/test_json_serializer.py

lbmpy_tests/test_shear_flow.py