Support JDBC "execute"

[JasonPierce]

Presently, node-teradata supports executeQuery via read() and readPreparedStatement(), and executeUpdate via write() and writePreparedStatement(). The JDBC API has a third method for executing statements called execute.

• executeQuery: executes SELECT statements
• executeUpdate: executes non-SELECT statements (e.g., INSERT, UPDATE, DELETE)
• execute: executes SELECT and non-SELECT statements. But, more importantly, it can execute multiple statements, which is something neither of the other methods support

Acceptance Criteria

1. New method execute executes one or more (read and/or write) statements within the query
2. New method executePreparedStatement executes one or more (read and/or write) statements within the query, using prepared statements
3. execute and executePreparedStatement returns an array of results:
   • One result for each statement within the query
   • Results are indexed by order of statement execution
4. Documentation is updated with examples