TODO

 * read/write $ElementNodeData
 * complete manual
    - sort reference by relevance not just alphabetically
 * pass long options to PETSc (fino --ksp_view -> pass -ksp_view to PETSc)
 * try to see if PETSC has OpenMP and parallelize the matrix assembly
    - choose OMP_NUM_THREADS from the input
 * add keyword PETSC_OPTION in input file to call PetscOptionsSetValue()
 * optimize assemblies -> gmsh partition
 * read tet4 (or hex8) and convert internally to tet10 (or hex20), or conversely
 * optimize code with const and restrict
 * log stages
 * AMR?
    - stressrefine
    - sparselizard
 * rewrite DEBUG as FINO_DUMP, write elemental matrices, gradients at gauss points, etc
 * compute heat fluxes
 * put mat2sng in a different code
 * see if some for loops can be replaced by matrix-matrix products
 * DMplex + mutigrid
 * extrapolate matrix for prisms
 * optimize memory usage with massif
    - instead of having max_neighbours try to get the actual number of neighbors per node
    - preallocation
 * non-linearities - detect them! an allow explicit settings LINEAR_BULK/NONLINEAR_BULK - BC/LINEAR_BC/NONLINEAR_BC
    - materials
       * bi-linear elastoplastic 
       * orthotropic heat conduction
    - BCs
       * type radiation
    - transient
       * check the time derivative of the mass matrix in thermal
       * be smart when to re-compute the matrices
    - geometries
       * total lagrangian
    - contact
       * hertz?
 * write a toolbox for FreeCAD
 * onelab integration
 * test suite
    - transient heat
    - modal
    - thermo-mechanical
    - parametric (cantilever)
    - multifreedom (radial, conic)
    - stress linearization
    - space-dependent properties