Checking Colormap Validity

• pxl-col-ccmap-valid_colormap: valid_colormap/1
• pxl-col-ccmap-valid_colormapable: valid_colormapable/2
• pxl-col-ccmap-ensure_valid_colormap: ensure_valid_colormap/2
• pxl-col-ccmap-ensure_valid_colormapable: ensure_valid_colormapable/3