Cubicspline added to the command tangent (also the tool)

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25389 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e
Test for changeset 25389

git-svn-id: http://dev.geogebra.org/svn/trunk/geogebra@25390 23ce0884-8a58-47d3-bc5c-ddf1cd5b9f9e