Reuse of ConnectionManager in DBCJ

- Reuse ConnectionManager via a ConcurrentHashMap **only** in DBCJ
- Some maven config file modified/fixed
- DBCJ update
  - Support pooled sync datasource [druid](https://github.com/alibaba/druid)
  - Support Statement
  - ResultSet index start at 1 (while adbcj start at 0 for iterators)
- Some tiny change