A lightweight browser for exploration of tomograms
    Basic usage: 
    1) loads an show an arbitrary tomogram 
    2) loads and shows the volume currently in exploration in tomoview or tomoslice.  
    % Shows a file (loading its content in memory!)
    dtmshow file.em;
    % Shows the contents of the volume currently explored in tomoview
    dtmshow -d x; to choose a viewing direction
     Visualizing big tomograms
     'on_the_fly','otf','i' :  
                       File name or catalogue query
                       The resulting window will not preload any part of
                       the volume in memory, but just download form the
                       hard disk each required slice individually.
                       - default: not active, full volume is loaded
     dtmshow -otf my_file.em
     dtmshow -otf @{default}1; % to access directly a catalogue entry.
     'slice', 's'    : choose the slice the program will open on.
     Visualizing tilt series
     'tilt_series','ts'   :  note that the file is a tilt series 
     'machinefmt','mf'    :  machine format for endianess
     dtmshow -ts file -mf
  dSlice, dpreview, dtmview