Fixed failure in GridDatasetInfo.writeGrid() when grid has no description
* This was causing NCSS to fail when displaying the dataset.html form.
* Improved reporting of exceptions in NCSS. This should make it easier to find other bugs.
Fixed CompositeStationFeature.subset() bug.
* This was causing NCSS to return observations outside of specified date range from some feature collections.
Fixed NcssShowDatasetInfoImpl conflict.