make numeric and interactive visualization tools obey the recursive flag

start visibility gui mods

physical entities can now be defined using a string instead of a number (and
there is a new field $PhysicalNames in the .msh format to keep track of these
strings)

- re-add names in visibility broswer (will change in the future)
- shorten tutorials

better tol in extrude

show how to mesh the volume from a surface STL

don't throw in test_move_point_parametric_triangle

better tutorial on transfinite grids

remove elliptic - same as Transfinite with Mesh.Smoothing > 1

- finished volume extrusion
- cleanup ExtrudeParam (plug memory leak + remove unused stuff)
- make netgen the default 3D algo for now (since it actually works)

make explicit regions in extrusions DEPRECATED

remove more attractor crap

remove aniso + old extrude from interface

fine tuning

fix off-by-one bug in the computation of u

forgot to add this

extrude edge+face (only "recombined" for now; we'll implement subdivision
into simplices "globally" later)

start work on extrusion

don't build metis and ann by default anymore

some initial steps before reimplemeting extrusion

todo tetgen: recategorize vertices+tets in each separate region

missing headers

small fixes for mesh opti

reimplemented mesh optimization -- seems to work nicely with netgen (grids
generated with tetgen seem to be wrong)