also fixes error handling for MeshEditor's StitchVertexLoopsMinimal (which I referenced for the hole filler's error handling, but looked broken)
#codereview ryan.schmidt
#rb none
[CL 6897337 by Jimmy Andrews in Dev-Editor branch]
- make FDynamicMesh3 constructor explicit because it allowed a temporary empty mesh to be constructed if FDynamicMesh* was passed to function that was expecting const FDynamicMesh&
- add FDynamicMeshEditor::DisconnectTriangles
- replace Polygon2/Polyline3 PointAt() with GetSegmentPoint() and GetSegmentPointUnitParam()
- add FPolyline3::SmoothSubdivide()
- add MeshIndexUtil, and function for converting Tri to Point indices
#rb none
#codereview jimmy.andrews
#rnx
[CL 6683551 by Ryan Schmidt in Dev-Editor branch]