changes for handling multiple imsets for echelle:

GetKeyInfo8:
	check opt_elem[0] to see if echelle data
	if echelle {
	    set echelle flag
	    remove comparison between nextend/3 and nrptexp
	    save nrptexp
	}

new routine:
	determine the correct value for nrptexp

SumGrps:
	for sporder = minorder, maxorder {
	    call PrGrpBegin, i.e. for output imset, not input
	    reset index to zero
	    find first imset matching sporder in array
	    if verbose, print input imset number
	    getsinglegroup (x)
	    while not done {
		find next imset matching sporder in array
		if verbose, print input imset number
		getsinglegroup (y)
		add to current sum (x)
		etc
	    }
	    update extension keywords
	    write output imset
	}

PutHdrInfo8:
	OK as is?  problem:  nextend could vary from imset to imset
	set nextend to nrptexp


new routine:
	if not echelle {
	    set all elements in array to one
	    return
	}

	read sporder from each SCI extension, saving the values in an array
	get delta_sporder (+1 or -1) by comparing the first two elements
	loop over all elements in the sporder array {
	    count the number of times sporder changes in a different
		    direction from the sign of delta_sporder
	    assign that value to nrptexp
	    find minorder, maxorder
	}