Simplify driver url

This pull request aims

* Simplify driver url configuration, currently from _production:hive:com.nflabs.zeppelin.driver.hive.HiveDriver:jdbc:hive2://_ to _production:hive2://_
* Remove Zengine dependency from Logical plan generation - Logical goes completely logical.
* Clear separation role of Driver and Connection like JDBC driver model does
* Hierarchical model for Lazy initialized, Classloader wrapped connection.