Support CF formatted netCDF

[BSchilperoort]

In a CF formatted netCDF, coordinates contain a "bounds" dim, which denote the left and right bounds of the interval. This should be supported by this plugin, and would actually save us from computing the bounds ourselves.

[DWesl]

In a CF formatted netCDF, coordinate variables might reference a "bounds" variable, which contains the boundaries of the cell, usually the lower and upper boundaries of a 1-D coordinate variable on a rectangular grid.
This should be supported by this plugin, and would actually save us from computing the bounds ourselves.

SGRID conventions allow for "face" and "node" dimensions, which you should be able to use in a similar manner.

Stripping all the attributes leaves something like this:

dimensions:
    face_x = 5;
    face_y = 5;
    edge_x = 6;
    edge_y = 6;

variables:
    float flux(face_y, face_x);
    float face_y(face_y);
    float face_x(face_x);
    float edge_x(edge_x);
    float edge_y(edge_y);

data:
    edge_x = { 0, 1, 2, 3, 4, 5 };
    edge_y = { 0, 1, 2, 3, 4, 5 };
    face_x = { 0.5, 1.5, 2.5, 3.5, 4.5 };
    face_y = { 0.5, 1.5, 2.5, 3.5, 4.5 };

CF-formatted data might also give you cell areas, which is likely what you want the boundaries for.