Free Space test cases + Nodal Interpolation + Small Fix in FunctionSpace: Bug with cell function in 2D for 3D Function Space + Vertices of GroupOfElement

tolerance cannot be choosen that large; in case of non-connected meshes we could end up interpolating too far outside the (wrong) element, leading to bad values

DDM Tests: Rewritting SystemAbstract::getSolution + FunctionSpace::getUnorderedKeys() + FunctionSpace::getAllDofs with set + FunctionSpace::getKeys(set)

useful for remapping a mesh onto a (slightly modified) CAD, for sensitivity analyses

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In that case we search for all the matches in the octree, and we try to return amongst those the element that matches the input coordinates.

We use this in MathEval so we can reliably make operations on discontinuous datasets (e.g. edge element vector fields), on identical meshes that were possibly reordered.