FX 8 3D: Change mesh arrays to observable arrays

Main idea of this issue is to improve TriangleMesh API up to the following form:

public class TriangleMesh {
    ObservableFloatList getPoints();
    ObservableFloatList getTexCoords();
    ObservableIntList getFaces();
    ObservableIntList getSmoothingGroups();
}

The open question is what would be those ObservableFloatList and ObservableIntList.