Added JDBC support to sql.reader

- classpath can be set in sql file, or via CLASSPATH environment variable
- user/password may be set via variable in sql file, or in jdbc url

Example SQL file:

    type: jdbc
    class: oracle.jdbc.OracleDriver
    classpath: /path/to/ojdbc5.jar
    user: scott
    password: tiger
    url: jdbc:oracle:thin:@myhost:1521:orcl
    query: select * from emp