add methods to DataQuery object for returning RequestDataset
dictionary lists

Two methods were added to the DataQuery object:
 1. get_package_datasets
 2. get_variable_or_index_dataset
These new methods replace the old approach of returning RequestDataset
dictionaries when a single row was returned. The previous methods (i.e.
get_package) will now always return a dictionary with keyed lists.
Merge branch 'master' of https://github.com/NCPP/ClimateTranslator