draw_2D_shad(ncfile, values, varn)
ncfile= file to use
values=[vnamefs]:[dimvals]:[dimxvn]:[dimyvn]:[dimxyfmt]:[colorbarvals]:
  [sminv],[smaxv]:[figt]:[kindfig]:[reverse]:[mapv]:[close]
    [vnamefs]: Name in the figure of the variable to be shaded
  [dimvals]: ',' list of [dimname]|[value] telling at which dimension of the
    variable a given value is required (-1, all the length)
  [dimx/yvn]: name of the variables with the values of the final dimensions (x,y)
  [dimxyfmt]=[dxs],[dxf],[Ndx],[ordx],[dys],[dyf],[Ndy],[ordx]: format of the values at each axis (or 'auto')
    [dxs]: style of x-axis ('auto' for 'pretty')
      'Nfix', values computed at even 'Ndx'
      'Vfix', values computed at even 'Ndx' increments
      'pretty', values computed following aprox. 'Ndx' at 'pretty' intervals (2.,2.5,4,5,10)
    [dxf]: format of the labels at the x-axis ('auto' for '%5g')
    [Ndx]: Number of ticks at the x-axis ('auto' for 5)
    [ordx]: angle of orientation of ticks at the x-axis ('auto' for horizontal)
    [dys]: style of y-axis ('auto' for 'pretty')
    [dyf]: format of the labels at the y-axis ('auto' for '%5g')
    [Ndy]: Number of ticks at the y-axis ('auto' for 5)
    [ordy]: angle of orientation of ticks at the y-axis ('auto' for horizontal)
  [colorbarvals]=[colbarn],[fmtcolorbar],[orientation]
    [colorbarn]: name of the color bar
    [fmtcolorbar]: format of the numbers in the color bar 'C'-like ('auto' for %6g)
    [orientation]: orientation of the colorbar ('vertical' (default, by 'auto'), 'horizontal')
  [smin/axv]: minimum and maximum value for the shading or:
    'Srange': for full range
    'Saroundmean@val': for mean-xtrm,mean+xtrm where xtrm = np.min(mean-min@val,max@val-mean)
    'Saroundminmax@val': for min*val,max*val
    'Saroundpercentile@val': for median-xtrm,median+xtrm where xtrm = np.min(median-percentile_(val),
      percentile_(100-val)-median)
    'Smean@val': for -xtrm,xtrm where xtrm = np.min(mean-min*@val,max*@val-mean)
    'Smedian@val': for -xtrm,xtrm where xtrm = np.min(median-min@val,max@val-median)
    'Spercentile@val': for -xtrm,xtrm where xtrm = np.min(median-percentile_(val),
      percentile_(100-val)-median)
  [figt]: title of the figure ('|' for spaces)
  [kindfig]: kind of figure
  [reverse]: Transformation of the values
    * 'transpose': reverse the axes (x-->y, y-->x)
    * 'flip'@[x/y]: flip the axis x or y
  [mapv]: map characteristics: [proj],[res]
    see full documentation: http://matplotlib.org/basemap
    [proj]: projection
      * 'cyl', cilindric
      * 'lcc', lambert conformal
    [res]: resolution:
      * 'c', crude
      * 'l', low
      * 'i', intermediate
      * 'h', high
      * 'f', full
  [close]: Whether figure should be finished or not
varn= [varsn] name of the variable to plot with shading