Inversion extension

[brandynlucca]

This first draft includes the initial code for:

1. Preparing scattering model and parameter values for $TS$ modeling (via pcdwba)
2. Computing $TS$ via the PCDWBA across all defined frequencies
3. Calculating the orientation-averaged TS at each frequency
4. Calculating the length-averaged $TS$ at each frequency
5. Converting to $S_V$

The unit tests have not been fully written; however, the outputs have been validated for a discrete set of inputs that are extremely close (i.e. < 0.0001 dB tolerance) to the outputs from the original MATLAB code. This draft does not yet include the inversion itself.