WCST_Import add color table to coverage's metadata

[Bang Pham Huu]

To have the colorPallete when encoding in TIFF as ​http://rasdaman.org/wiki/CommonFormatsInterface

color table should be added as an option in the ingredient, 
pointing to a file. When that is present, the contents of that file
should be added to the coverage's metadata (only once) 
under a special tag: <colorPaletteTable>

Usage in WCST_Import for general recipes, example:

          "metadata": {
            "type": "json",
            "global": {
              "Title": "'Drought code'"
         	  },
                  "colorPaletteTable": "PATH/TO/color_palette_table.cpt"
             }
           }