moving a lot of opengl-specific annotation into new gl render surface.
fix crashes on degenerate shapes in simple volume renderer.
new option in simple volume renderer to only sample within tet.
this is a big speedup (3x) for very small meshes, but for very
large meshes can be a small (<10%) penalty.
ignore degenerate tetrahedra
moving 2d text rendering code into render surface.
adding start of world space annotator and use it for 3d axes, bbox.
Merge branch 'master' of github.com:jsmeredith/EAVL
allow 3d lines to bump themselves slightly forward
starting world text annotations.
moving remaining text annotation opengl specifics into world annotator.
should be using pre-transformed coords to determine axis extents.
removing no-longer needed opengl textures from base window class.
using annotator instead of opengl for radial axis.
adding start of postscript rendering chain.
Merge branch 'master' of github.com:jsmeredith/EAVL
further segregating opengl-specific texture things.
start moving opengl commands out of view class.
finished removing opengl code from non-opengl rendering paths.