Sns gq updates

[pshriwise]

These updates are a result of our experience translating a native SNS model:

• Adding support for GQ ellipsoid
• Adding case-by-case reduction of GQ types to more CAD-friendly types if they are geometrically equivalent or near a transition. This is usually based on a near-zero coefficient.

With this PR the GQ types now supported are ELLIPSOID, ELLIPTIC_CONE, and ELLIPTIC_CYL

[gonuke]

Do we have any tests for this? I know that

• mcnp2cad is sorely lacking for tests,
• we've discussed how to do this before
• it's hard to do
• I don't have a huge appetite for comprehensive testing at this time

but, I have know way to judge this addition...
Maybe @makeclean should take a look.

[pshriwise]

Sadly no we don't have any tests for these changes. They have shown to be effective in reducing GQ types to something more CAD-friendly in a lot of cases with near-zero second order coefficients or RHS values. The beginning of this new workflow made translating two relatively complex models from Steve Liley (ESS and ISIS) with 20+ GQs. Though I will admit that, while better, this workflow still relies on tolerance values to get the right answer.

[gonuke]

This appears to have been merged in other places during swapping between repos.