Changes for #154 - Enhanced Support for Optimistic Locking

This pull has several fixes for issues raised in #154:

1. Enhance @SelectKey to support multiple key columns (like the existing support with JDBC generated keys)
2. Enhance <selectKey> to support multiple key columns
3. Allow select key and generated keys in update statements

Two tests are marked as ignored because HSQL is not returning generated columns after an update statement.