Vertical structures on the bottom in TELEMAC-3D

This issue was created automatically from an original CUE issue, opened by Agnes Leroy. Further discussion may take place here.

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This new feature aims at making TEMEAC-3D able to represent vertical structures on the bottom (like steps, submerged piles, etc.).
The chosen approach is to let the number of planes per 2D point vary in space.
The planes below the steps will always be fixed.
Wall boundary conditions will be applied onto the boundaries of the vertical structures.
Most of the developments have been done by Pengze Wang during an internship at LNHE.