Update the bathymery based on GEBCO 2020 data. Add land river colouring.

Textures/Globe/01READMEocean_depth_1png.txt

@@ -1,10 +1,15 @@
  This texture uses ETOPO1 data from "http://www.ngdc.noaa.gov/mgg/global/global.html:
  http://www.ngdc.noaa.gov/mgg/global/relief/ETOPO1/data/bedrock/grid_registered/georeferenced_tiff/
+ and Global ocean & land terrain models 2020 (GEBCO_2020 Grid - Data GeoTiff):
+ https://www.gebco.net/data_and_products/gridded_bathymetry_data/
  in the alpha channel, and parts of world.topo.bathy.200407.3x4996x2048.png in the rgb channels
  and 'Cross Blended Hypso with Shaded Relief, Water, and Drainages' from "http://www.naturalearthdata.com/downloads/10m-raster-data/10m-cross-blend-hypso/"
  See 00README.txt in the same folder for information about the image usage policy of world.topo.bathy.200407.3x4996x2048.png
+
+--
  Data from Natural Earth is in Public Domain.
 
+--
  How to Cite ETOPO1:
  Amante, C. and B. W. Eakins, ETOPO1 1 Arc-Minute Global Relief Model: Procedures, Data Sources and Analysis.
  NOAA Technical Memorandum NESDIS NGDC-24, 19 pp, March 2009.
@@ -18,3 +23,23 @@
  to copyright protection within the United States unless specifically annotated
  otherwise (copyright may be held elsewhere). Foreign copyrights may apply.
 d
+
+---
+The GEBCO Grid is placed in the public domain and may be used free of charge.
+
+Use of the GEBCO Grid indicates that the user accepts the conditions of use and disclaimer information given below.
+Users are free to:
+
+    Copy, publish, distribute and transmit The GEBCO Grid.
+    Adapt The GEBCO Grid.
+    Commercially exploit The GEBCO Grid, by, for example, combining it with
+    other information, or by including it in their own product or application.
+
+Users must:
+
+    Acknowledge the source of The GEBCO Grid. A suitable form of attribution is
+    given in the documentation that accompanies The GEBCO Grid.
+    Not use The GEBCO Grid in a way that suggests any official status or that
+    GEBCO, or the IHO or IOC, endorses any particular application of The GEBCO
+    Grid.
+    Not mislead others or misrepresent The GEBCO Grid or its source.