Allow the country field in addressbook to be specified as either the ISO 2 character country code or the netsuite enumeration value. 

ex: `addressbook.country = “_unitedStates”` and `addressbook.country = “US”` have the same end result.
Merge pull request #1 from charitywater/country-enum

Updated the country field in addressbook to be specified as either the ISO 2 character country code or the netsuite enumeration value.