Make Connectors Dynamic

[QuentinTorg]

Currently, when connectors are added to a project a hull is created the input points and the geometry is fixed from that point on. This means that users need to know that all of their parts must be in position before they can add connectors.

It would be far better if connectors were dynamic, so a user could add connectors, then move an object and the connectors would move with it.

To make this happen, the Connectors object should contain some sort of list of points that is mutable. When points are added, they should work as pointers to the object that they were linked to. Usually, points are part of a Hull() object in an object, so they should continue to be pointers to the same element of the hull even when the hull is traslated or rotated. The sl.hull() command will not be called until a solid is requested from the Connector object using Connector.solid() is called.