Name vertical level interpretation

This PR parses NAME 'z column heading' using regular expressions.
Result is a versatile (whitespace agnostic, integer/float agnostic).
It is also strict, in the sense that it does not consider anything other than a match that can differ by only whitespace.

Still to be decided whether bounds are to be automatically guessed for NAMEIII files, since points are defined not bounds, while bounds are defined not points for NAMEII.  Guessing bounds will allow cubes from the two formats to be merged.