algo2d=triangle is not available at the moment

- polish gui for interactive visibility
- upgrade tetgen to latest available version

deprecated -> warnings instead of errors

fix message

make sure we don't store physical tags multiple times per entity

add "Show with the mouse" mode in interactive visibility. This is awesome :-)

don't throw an exception if attributes are not defined -- just issue an error

make sure the boundary vertices are ordered consistently with the
ordering of the transfinite corners. If not, just revert the list.

This is crucial for maintaining backward compatibility with the old
version.

print warning for now when extrusion mesh is not recombined

algo to compute normal for plane gmsh surfaces was wrong (sign could be wrong)

slightly better fix than before

add extra arg to XYZtoUV so we can use it also for point that are not on
the surface

- revert convergence check on xyz error in xyz2uv: just issue a warning

- remove computation of mean plane during meshing: it's not used anymore
(we only use the mean plane for plane Gmsh surfacesm and it is already
computed correctly in the gmshFace constructor)

temporary (?) fix for transfinite on tri

make default transfinite subdivision match old version to minimize
backward compat problems

done transfinite volume

reimplemented transfinite volume meshing algo (not complete yet)

add easy "show all" butt in interactive vis gui

remove unused stuff + invert default sorting order in vis browser

forgot to classify vertex in STL reader

more on clcurv options

new option to compute char lengths from curvature + removed most unused mesh options

curvature control is ok
divide and conquer algo has been cleaned up

fix align

finished implementation of numeric+interactive visibility stuff for physicals

fix netgen optimization (need tets with neg vol)

allow unconstrained background meshes