bug with spline generation
namespace physics::classical_mechanics

created functions to transform from period to angular frequency and back
complex utilities

functions to take  complex vector and split it into two vector of doubles (real and image).  Also added a utility function that will take a modulus and phase/arg of a complex number
and return the complex number.
moved file
initial guess of a harmonic phase and amplitude/offset
renamed header file
depricated cosfit/cosfcn functions