GENIE Gridspec Diagrams Mosaic

A mosaic consists of one or more "mosaicgrids". A mosaicgrid can either be a child mosaic, or a grid tile. Using this recursive mosaic concept, it is possible to represent a hierarchy or "tree" of grids for an entire framework of Earth system models, with each grid eventually ending with tiles as the "leaves". An optional grid descriptor may be used to apply a description to all tiles within a mosaic grid, e.g. "regular_lat_lon", "cubed_sphere".