Some documentation fixes, new gradients (black to white, white to black and blue-white-red) defined and used for new variables in PNGIO (P, ALB and DW). A bug has been fixed for ILWR in GRIBIO as well as a bug when converting geographic coordinates to rotated ones.

New options have been added to the undercatch filter, allowing to specify the temperature thresholds with the CST argument (to make it more similar to GeoTop).