atlab mesh object
    VarType = node or element (for elements, one needs xc and yc from
    FVCOM NC file. Not implemented yet.


 OUTPUT:
    transect = Matlab structure with indices

 EXAMPLE USAGE
    [transect]  = transect_nodes_screen(Mobj,'nodes')

 Author(s):
    Ricardo Torres and Geoff Cowles (University of Massachusetts Dartmouth)

 Note:
    Uses ginput2 which allows zoom/pan before selecting points and displays
    clicked points realtime

 Revision history

=================