Simplify CFDMesh Bezier_curve to minimal implementation.

Remove unused methods in Bezier_curve class.

Although these methods aren't causing any harm, as I look to use VspSurf
and VspCurve to replace as much of this as possible, it makes sense to
trim things down to minimize porting effort and maximize understanding.
Remove unused methods from SCurve
Clean out old commented code.
Refactor SurfCore out of cfd_mesh/Surf.
Eliminate unused 01 methods in SurfCore.  Change scope of 2nd deriv methods.
Clean up SurfCore includes
Clean up SurfCore.cpp
Split CleanMergeSurfs out of CfdMeshMgr::ReadSurfs
Switch SurfCore from local Bezier implementation to one from Code-Eli.
Change SurfCore to use Code-Eli's native umax/vmax values preparing for non-cubic surfaces.
Eliminate uses of SurfCore.GetNumU switching to GetNumUPatches (and W)
Remove m_NumU/W number of control points from SurfCore
Move manipulation of BezierCurve control points into BezierCurve for FlipDir()
Implement BezierCurve::first/last_pnt() avoiding external control point access.
Simplify Bezier_curve interface.  Eliminate init_num_sections and put_pnt, replacing with put_pnts.
Convert Bezier_curve to thin wrapper on Code-Eli
Trial use of Code-Eli's built-in fitting instead of buildCurve's implementation
Make cfd_mesh Surf more consty
Make cfd_mesh SurfCore more consty
Add consty Surf::GetSurfCore()