Refined when nodes are hilighted.

Nodes are now hilighted at morespecific times. The node edit window also
dissapears at certain times.
Split the GUI into separate files.

Additionally:
	-Somewhat improved imports
	-Gave the matrix class a more stable definition of "=0"

Implementation:
	There are now 4 GUI files. A truss display class, a truss
	modification tools/controls class, a common User Interface States
	class (essentially an enum/constant list), and a top level class
	which pulls the two components together, and makes the menu
	(save/load) bar.
Added Delete Member feature.
Changed the Nodes so they could only handle one load.

Also allowed command-lie loading of trusses