DHFactor and ETS3

This fails, tool transform fails to be handled properly by dh.command
 
```
L1 = 5; L2=4; L3 = 3; L4 = 2;
dh=DHFactor( 'Tz(L1)*Rz(q1)*Tx(L2)*Rx(q2)*Ty(L3)*Ry(q3+pi)')
r = eval( dh.command('myrobot') )
r.tool=troty(pi)*transl([ 0 0 L4])
r.plot([0 0 0])
```

