Graphical representation of contents in a table.
  This function provides (roughly) a command line version of "tableview".
   - Orientation distribution.
   - Spatial distribution.
   - Formatting into Chimera.
   - Simple plots, histograms and scatterplots.
   - Fast access to the usual depiction modus using flag "profile"
   - Interactive plots tha allow picking and visualization of particles on
     screen .
  'table'               table, as variable or filename (.tbl extension can be skipped).
                        You can also pass a set of tables
                        each one will generate a different figure.
      dtrandom 10 -o t1.tbl -rg 100;
      dtrandom 10 -o t2.tbl -rg 100;
      dtplot t1|t2 -l tag;
      % plots the orientation of the two tables and marks the tags
      'tags'                   :  restricts the table to a set of tags.
      'table_restrict', 'tr'   :  passes a table restriction
                                  (as explained in table_grep)
      dtplot example.tbl -tr 30