FUNCTION: LieTools/DDiagram
USAGE: DDiagram(Gt), DDiagram(); DDiagram(Gtype,rnk);
SYNOPSIS: DDiagram(Gt) displays the Dynkin diagram of a semisimple
  Lie algebra Gt.  DDiagram can also be called without employing the
  any argument Gt but this usage requires a previously initialized global
  Lie algebra environment. (See LieTools[gSetup].)
EXAMPLE: 
> LieTools[DDiagram](E6);

           2
           |
   1---3---4---5---6


SEE ALSO: Coxeter[Diagram]
