Roeland's recent improvements - especially a more robust Mesh::Derivatives().

--
user: Michael Guravage <michael.guravage@cwi.nl>
branch 'default'
changed src/VirtualLeaf.pro
changed src/build_models/plugin_test.pro
changed src/cell.cpp
changed src/cellbase.cpp
changed src/cellbase.h
changed src/mesh.cpp
changed src/mesh.h