Drop-in replaced Scott Socolofsky's depths.py and roms.py using new_depths.py stretching, etc.
Major changes/refactoring to depths, including:
    Taking out the get_Vstretching_[1-4] and get_Vtransform_[1-2] functions from the (now)
    wrapper functions.

    Added depths wrapper functions that calculate the zrho, zw, or dz array in one command.

    Significant documenting and debugging.