[FEAT] 3D Interpolation Scheme in Grid

[aaronjridley]

Is your feature request related to a problem? Please describe.
In order to implement things like satellites and multiple grids that share information, a generalized 3D interpolation scheme needs to be created. The general 3d interpolation needs to be independent of the grid. Then, it needs to be connected to the grid.

Describe the solution you'd like
Functions that should be created:

• grid.set_interpolation_coefs(lons, lats, alts)
• grid.get_values(3darray_on_grid)
• These will depend on a bunch of other functions that are more generalized
• Could feed in a hook/reference, so that the grid could store multiple sets of interpolation coefficients

Describe alternatives you've considered
Need some generalized functions too, so that we can interpolate things like boundary condition files (e.g., lower BCs, electrodynamics files).

Idea: If we use the grid architecture (class), then we should be able to create a mapping from one grid to another. We could then create a general function that is something like grid1.create_interpolation_coefs(grid2). We may want to have a "name" variable in each of the grids, so when the mapping is done, the grid1 can keep track of the different mappings.

[aaronjridley]

I think that this works fine. We need to add some documentation to discuss how it can be used, but this works.