Implemented changes requested by @tlunet

pySDC/helpers/spectral_helper.py

pySDC/implementations/problem_classes/Burgers.py

...implementations/problem_classes/HeatEquation_Chebychev.py

pySDC/implementations/problem_classes/RayleighBenard.py

pySDC/implementations/problem_classes/generic_spectral.py

pySDC/tests/test_helpers/test_spectral_helper.py

...ts/test_helpers/test_spectral_helper_1d_ultraspherical.py

pySDC/tests/test_problems/test_Burgers.py

pySDC/tests/test_problems/test_heat_chebychev.py