FUNCTION: LieTools/G2E
USAGE: G2E(i);
SYNOPSIS:  G2E converts root labeling from 1..dimg to -nprts .. +nprts
CAVEATS: requires a previously initialized global Lie algebra environment.
  (See LieTools[gSetup].)
EXAMPLE: 
> LieTools[gSetup](G,2):
Setting up Gtype = G   rnk = 2
> LieTools[G2E](1);

                                  -6

> LieTools[E2G](-6);

                                  1

SEE ALSO: LieTools[E2G], LieTools[G2R], LieTools[R2G]
