Some code hygiene.

src/angularbasis.cpp

src/angularbasis.hpp

src/atomicspectrum.cpp

src/atomicspectrum.hpp

src/basis.cpp

src/basis.hpp

src/cutoff.cpp

src/cutoff.hpp

src/functions.cpp

src/functions.hpp

src/options.cpp

src/options.hpp

src/power.cpp

src/power.hpp

src/radialbasis.cpp

src/radialbasis.hpp

src/spectrum.cpp

src/spectrum.hpp

src/structure.cpp

src/structure.hpp