GENIE Gridspec Diagrams Discretisation

The following grid tile discretisations should be supported by the gridspec. Currently the gridspec only provides support for logically rectangular grids (LRGs), with limited support for unstructured grids; Balaji proposes that the gridspec should be extended by the appropriate domain experts to cover other discretisations.

  The way a grid tile is split into cells, e.g. logically_rectangular.         

Note: the gridspec overview contains introductory and background information on the gridspec; more detailed information can be found in Balaji's gridspec document on the Earth System Curator website.