Truss variables in genLib
In genLib we can design and simulate trusses at low level, and we have a strict naming convention on truss variables to avoid mixing things up
To the right a simple truss is initialized and plotted. The truss is fully defined by two arrays
 Node array  xyz coordinates of all nodes
 One node for each row, node number is row number
 Variable name  N
 Edge array  node connections represented by node numbers
 One edge in each row, edge number is row number
 Variable name  E
If the truss is to be FEM simulated we need to specify the stiffness of each edge
 This is done be specifying the edge cross section area of each edge in column number 3 in the edge array
