Add optional JSR-310 support library (refs #222)

- scalikejdbc-core library should work not only Java8 but 6 and 7
- Add scalikejdbc-jsr310 for Java 8 users
- Remove depreacated methods from scalikejdbc.WrappedResultSet
- This change should be released as 2.1.0 due to API incompatibility