Add a new metric computation for level set, simply based on ls gradient and hessian eigendirections.
meshAdapt was modified to receive and intersect multiple metrics, preserving the most anisotropic metric.
Also added input and output functions to dgDofContainer, for the "NodeData" format.
Benchmark for anisotropic adaptation to level set iso-zero created in benchmarks_gmsh/LSIsozeroAniso.

First iteration on CGNS structured mesh loading, with (if expert mode is on) possibility to create high-order meshes from CGSN meshes.

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- if the XY view exists, juste change the data
- if not, create it

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Worked a lot oncurvilinear meshing : projection of point on surafces work, matching meshes andgeometry works better, added some test examples...

Make sure to close the files left open (on purpose) in ParseFile when we exit OpenProject or when we call ClearProject.

Leaving the files open can lead to file handle exhaustion, e.g. with onelab when remeshing several hundred times. This then leads to
unpredictable socket errors.