what is done for ellipse arcs in the built-in kernel. Fixes #578.

Interface OCC sewing algorithm in the creation of surface loops, with extra arg in API or "Using Sewing" keywords in .geo files (fixes #583)

- new ClassifySurfaces command in .geo files
- apply same workflow in classifySurfaces as in the interactive classification editor
- don't call createTopology in createGeometry anymore
- use STL in t13

document the fact that opencascade does not allow to create ellipse arcs with identical major and minor radii (fixes #578)

new mesh::clear()

Rationale: setNodes/setElements were intrinsically a bad design choice,
as these functions had to delete nodes and/or elements before storing the
new ones. Using these functions in the wrong way could lead to an invalid
mesh, with elements pointing to nodes that were deleted (in an adjacent
entity).

The only viable workflow is to delete the mesh (with the new clear()
function), before adding nodes/elements.

This reverts commit 07cc55d9

This reverts commit 211fa521, reversing
changes made to 8ba56d73.

make "preallocate*" and "*nativePointer" api functions only available in C and C++ (they don't make sense in Python and Julia)

modify getJacobians, getBasisFunctions & co to take integrationPoints directly as argument (instead of integrationType)

- document getBoundingBox when dim and tag are < 0

make getElementByCoordinates return local parametric coord in element + add optional args to force the dimension and request "strict" search (without tol)