Began work on implementing C++ code for reverberation.
- Renamed reverb_model to reverberation_model
- Added classes for eigenverbs and the monostatic/bistatic reverberation cases
- Added getter for spreading_model from wave_queue
- Added getter/setter to wave_queue to determine the origin of the wavefront
- Modified spreading_model to now have two new virtual functions used for reverb
- Changed calls inside of reflection_model to use new reverberation callbacks
- Reverberation_model now has three virtual functions.
	- Two to accomidate ease of the book keeping of surface and bottom collisions
	- One to compute the actual reverberation curve.
- Began modifications to spread_ray to accomidate new virtual functions from spreading_model