Fix NetCDF output for module-hfelem
This branch fixes an invalid array index exception in ncVar.cpp:
mbdyn -e -f harmonicExcitationElem3.mbd
terminate called after throwing an instance of 'netCDF::exceptions::NcInvalidCoords'
what(): NetCDF: Index exceeds dimension bound
file: /home/reinhard/install/netcdf-cxx4/cxx4/ncVar.cpp line:1049
In case of the multiplicative angular frequency step, there might be one frequency less in the output file. hfelem.pdf