dlink/observe vs jslink

[chrisjsewell]

Need to understand this a bit more deeply, in particular

• js linking only seems to work if a GUI has been instantiated (i.e. not for create_jsscene_viewf, create_jsmesh_view, create_jslabelmesh_view on their own). I guess this makes sense if the browser is doing the linking?
• currently color and transparency traits can't be jslinked, since they require an initial transformation (i.e. function call). This is talked about here: Extending jslink? jupyter-widgets/ipywidgets#1109
• Think about how the entire scene/gui callbacks could be client side

Some info here:

• http://ipywidgets.readthedocs.io/en/latest/examples/Widget%20Events.html#The-difference-between-linking-in-the-kernel-and-linking-in-the-client
• http://ipywidgets.readthedocs.io/en/latest/examples/Widget%20Custom.html