Implement nD-NDT sensor model in Beluga

[hidmic]

Feature description

Connected to #93. Depends on #309. Precisely what the title says. Craft a likelihood function by matching a point cloud with an NDT map. Good performance is crucial, so make sure to micro benchmark it. Optimizations for the 2D and/or 3D case are also valid.

[hidmic]

As of #338, we have a first 2D variant. I'll keep this one open until we land a 3D variant.