Add analytic mode-by-mode solution (AcousticFieldSoftCylinder)
Add the mode-by-mode solution for the AcousticFieldSoftCylinder case ( std::complex used for complex-number operations, instead of the home-made structure 'cplx' )
Add the mode-by-mode solution for the AcousticFieldSoftCylinder case ( std::complex used for complex-number operations, instead of the home-made structure 'cplx' )