Improve shapecast range intersect function return options

[gkjohnson]

Related to #228, #218, #173

As of #228 the intersectsRange function is allowed to return true or false. false causes traversal and triangle iteration to continue while returning true stops traversal and prevents triangle traversal.

Examples like collectTriangles, selection, and sculpt might benefit from more granularity to prevent triangle iteration while still continuing traversal which would prevent unnecessary reading of the triangle vertices when they aren't being used.

• Add three states that can be returned: CONTINUE_TRAVERSAL, SKIP_TRIANGLES, INTERSECTED

[gkjohnson]

Alternatively all those examples could use intersectsRange instead which would likely improve performance. The collectTriangles example would require exposing SeparatingAxisTriangle publicly, though.

Change class name to ExtendedTriangle.

[gkjohnson]

Unneeded, I think, with the solo intersects range function.