Editing STEP importer improvements


STEP is the current standard for exchange of CAD data between different software packages.  BRL-CAD makes use of the NIST STEP Class Libraries code to support its step-g converter, but the converter is still in its infancy.

The importer should at least be updated to preserve the geometry hierarchy during import.  Right now, the converter only imports a subset of NURBS geometry.  Support needs to be added for importing non-solid NURBS geometry, polygonal geometry, unorganized triangle mesh geometry, and implicit CSG geometry. 

Specific items to remember:

* The libraries should compile with strict compiler flags, as used in recent BRL-CAD compilations.
* BRL-CAD makes use of the doxygen system for source code documentation, so organizing source code documentation in the step libraries to work well with doxygen should be part of the review and updating process.

=References=

* src/conv/step

=Requirements=

*Familiarity with C++