Auth: cjf

Connections: From Layout Engine to Data Manager, Event, Graph

The Layout Engine will be responsible for repositioning the elements in the
Graph to make them presentable in a GUI.  It will do so by accessing the
Graph through the Data Manager to get at the Objects stored in them.  It will
build its own internal representation of the graphical system so that it
can arrange them properly, and when it has found a good layout, it will send
a stream of events to the Data Manager with repositioning information in them.
In this way, it will rearrange the items on the screen.