document the new material property infrastructure.

this work is the culmination of a capston engineeering project from
TAMU students Trey Dinges, Cole Connelly, Vincent Olivarez, Chris
McGregor, Alex Studwell, and Reid Wilson.  they worked on implementing
a new BRL-CAD database entity type for storing material properties (a
'material' object), a new material command in libged, and updates to
rtweight, gqa, and art to use the new material objects.

does need to be reconciled with the other material property mechanisms
(.density vs _DENSITIES vs material objects) and the 'mater' command
itself, but material objects are the only way to pass advanced shaders
to our new 'art' appleseed PBR renderer.  material objects can have
different sets of material properties including physical, mechanical,
optical, thermal.

NEWS

@@ -9,6 +9,14 @@ first and are grouped by release.  Each release also includes optional
 descriptive text that emphasizes or further describes significant
 changes made.  See document footer for additional details.
 
+----------------------------------------------------------------------
+--- 2021-XX-XX  Release 7.34.X                                     ---
+----------------------------------------------------------------------
+
+* new 'material' command and material object infrastructure
+        - Dinges, Connelly, Olivarez, McGregor, Studwell, Wilson
+
+
 ----------------------------------------------------------------------
 --- 2021-XX-XX  Release 7.32.6                                     ---
 ----------------------------------------------------------------------