Lists of ints or strings for prepared statements.

This edit should enable passing vector&lt;cql_int_t&gt; and vector&lt;std::string&gt; to be bound as prepared query parameters of Cassandra-types list&lt;int&gt; and list&lt;text&gt;.
More list types could be added analogously, although some type generalization would be nice, otherwise there would be lots of almost-multiplication of code for the types and list encoding...