* Added "101010101" to list of known dummy dates, to avoid a crash in
HRDLPS file conversion.
* Added "TRAF" to the list of known surface fields, so it gets
annotated with the appropriate surface types.
* Renamed "sea_ice" to "lake_ice_or_sea_ice" in the list of surface
types, which is a more accurate description for the model data.
* Removed the "units" attribute for unitless level types. This was
originally added for COARDS compatibility, but is causing issues with
some netCDF utilities like Iris.
* When using --vardict or --opdict, put the definition string in an
attribute named "definition_opdict" instead of "description".
Suggested by Daniel Deacu.
* Fix a bug in metadata files which give units of "1" - it was getting
encoded as a numeral 1 instead of a string, causing grief with some
netCDF tools.