Let Scene encodes SceneElement as object instead of reference/pointer
Let Serializable StaplingDemo load a scene instead of SceneElements
Move common data used by Examples into a common folder to save space

ExampleStapling and SerializableStapling share the same external data
files. There's no need to duplicate the data files.
Add back missing 'obj' files.
Exclude collision detection between the wound and the arm
Clean up StaplingExample

1. Use 'filename' directly instead of retrieving the name from a
   MeshShape

2. Remove unnecessary output code (YAML and <fstream>)

3. Not using the name of a SceneElement as prefix when naming components