Fixes many bugs with curves

[JR-Morgan]

• Several improvements to NURBS conversion ToNative and ToSpeckle
  • Receiving NURBS from rhino should be perfect!
  • Sending Non-Bézier NURBS should also work perfectly!
  • Still some issues with sending Bézier nurbs. (see ➰ Add support for Bézier Nurbs curves #153)
• Added displayValue for nurbs curves so that they can now display in the viewer.
  • Still need to add the same for Bézier curves (see ➰ Sent Bézier curve are missing DisplayValues #152)
• Added Ellipse & Circle to native (Bézier) conversion

Before:

After:

Truth:

see #131