Temporary fix for CASSANDRA-8326

This has not been reviewed or well tested.  It's a temporary fix until a
proper patch can be put together and tested.
Merge remote-tracking branch 'thobbs/CASSANDRA-8326-temp-fix' into PYTHON-185

patch by thobbs
Assign key aliases from json, restore guard against empty string
Lookup cf_col_rows once, with a default value

fixes a problem trying to iterate 'None' when the cf has no rows in col_rows
Disambiguate row parameter in list comprehensions from function argument
Disambiguate row parameter in list comprehensions from function argument
Merge pull request #226 from datastax/PYTHON-185

PYTHON-185 - Handle upcoming schema meta changes