[CF-metadata] Array Subscript Convention

[Jonathan Gregory]

Dear Tom

Instead of introducing a separate attribute, perhaps we could indicate in the
standard names of the quantities themselves what their numbering convention is?
Presumably you will need standard names to identify the various arrays of
indices? If so, including the convention in the name seems analogous to
including "upward" and "downward" in vertical velocity components, for example.
Making it part of the standard name means you can't avoid including it.

Cheers

Jonathan