draw_stations_map(filename, values)
Function to plot a map with the stations
  filename= name of ASCII file with the values of the stations as: ('#' comments)
    [sttype],[label],[lon],[lat],[height]
      [sttype]: type of the station
      [label]: label of the station (LaTeX format, 'None' for no label)
      [lon]: longitude of the station
      [lat]: latitude of the station
      [height]: height of the station
  values=[stypevals]:[mapvals]:[SWNEbox]:[imgtit]:[imgkind]:[close]
    stypevals='@' separated list of [sttype]|[marker]|[color]|[size]|[fontsize]
      [sttype]: label of the type of the marker
      [marker]: type of the marker
      [color]: color of the marker
      [size]: size of the marker
    mapvals= 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
    SWNEbox: ',' list of the vertexs of the map [SWlon, NElon, SWlat, NElat]
      'lonlatxtrms': to use the extremes of the lon,lat stations
    imgtit: title of the image ('!' for spaces)
    imgkind: kind of file output of the image (ps, pns, pdf, ...)
    close: whether figure should be closed or not