Add WCHAR support using UTF16 package; fixes #13

For #13, it turns out that the return was an SQL_WVARCHAR, which is encoded as UTF16, not UTF8.  This seems only to be the case for things like "show table".

This patch adds support for UTF16 return types using the UTF16 package.  It works for me, but please look it over to see if I might have missed something or if it needs more conversions--it's late, and I might have missed something.  Or let me know if you have a different/better way to handle incoming UTF16 strings.