[QA] Add georeferencing tests on the CHS reference surface

[glabmoris]

We have MBES data on the CHS reference surface. See how this compares to MBES-lib in unit-tests

[JordanMcManus]

One way to do this would be to define a grid on the surface. For each cell, extract a mean depth (which is relative to geoid, if I recall correctly).

Then georef with MBES-lib. Then apply the same grid and extract a mean depth for each cell (which is relative to ellipsoid).

The difference for each cell should then be the geoid separation (with possibly tide variations which can be looked up).