Use Interpolations.jl for interpolating the 3D wind field.

[ufechner7]

Not yet implemented, which means the wind vector is "jumping" a little bit every 2m of movement of the kite. The following Python code needs to be translated:

           x_wind = ndimage.map_coordinates(self.u_pre, [[x1], [y1], [z1]], order=3, prefilter=False)
           y_wind = ndimage.map_coordinates(self.v_pre, [[x1], [y1], [z1]], order=3, prefilter=False)
           z_wind = ndimage.map_coordinates(self.w_pre, [[x1], [y1], [z1]], order=3, prefilter=False)

The file that needs to be updated is windfield.jl. This also requires unit tests and performance testing.

[ufechner7]

The' interpolate=true` keyword now works, but it provides only linear interpolation.