- started adding "snapping" to scale & rotate
 * scale is mostly done, though the snap values would need to be different
from those of translate
 * rotate snap is in progress
- removed the generateRenderables methods of the various sub classes of Part:
 * now all handled by the method in Part itself

- added experimentation with connectors:
 * for now just added visualization of connectors (via renderables)
- added cleaner visual for connector
 * also updated to the "generateRenderables" api
 * added some notes on what the basics for connectors should be