Point-in-mesh containment check which treats mesh as solid

This could use ray casting.

## Workaround

```rust
fn mesh_contains_point(mesh: &TriMesh, point: &Point3) -> bool {
if !mesh.aabb().contains_local_point(point) {
return false;
}

match mesh.toi_and_normal_with_ray(
&Isometry3::identity(),
&Ray::new(*point, Vector::new(T::one(), T::zero(), T::zero())),
false, // unused
) {
Some(intersection) => mesh.is_backface(intersection.feature),
None => false,
}
}
```

## Issues

1. Assumes mesh is well-formed (watertight and correctly wound)
2. Depends on ray casting for point queries, which is not necessarily ideal for keeping things modular