Eric and Mark plot some BMI updates

[mdpiper]

@mcflugen and @mdpiper talked BMI today, mostly in response to a comment @hrajagers added to #90.

I'll thread our ideas below.

[mdpiper]

Rename get_grid_rank to get_grid_dimension_count. "Rank" is a linear algebra term, and maybe not quite appropriate for describing model grids. The new name is also analogous to the existing get_grid_node_count.

[mdpiper]

Deprecate get_grid_size in favor of the existing get_grid_node_count.

[mdpiper]

Deprecate the get_grid_[xyz] functions in favor of a single new get_grid_node_coordinates function. This is discussed in #88.

[mdpiper]

Following the naming pattern set with get_grid_node_coordinates, rename get_grid_dimension_names in #90 to get_grid_node_coordinate_names. I think this follows the spirit of @hrajagers' comment.

[mdpiper]

Also following the naming pattern set with get_grid_node_coordinates, rename get_grid_units in #89 to get_grid_node_coordinate_units.

[mdpiper]

After more discussion in mid-December, we're going with get_grid_coordinate_units. It's a little shorter.

[mdpiper]

Make an "experimental" branch on https://github.com/csdms/bmi for us to work with the changes described here in the babelizer, for example.

We should also make sure to maintain docs for BMI 2 and 3.

[mdpiper]

I made the "experimental" branch in late December: https://github.com/csdms/bmi/tree/experimental.