TAJO-1109: Separate SQL Statements from Catalog Stores

This is a re-created pull request for this request, https://github.com/apache/tajo/pull/201.
I understand your concerns about maintaining upgrade sql fragementations in tajo project. Yes. It is difficult to keep the current version of sql codes. However, code about upgrade support is derived from my user experience. When I was a newbie in tajo, it is difficult for me to finding tajo tables and any related schema objects in existing RDBMS. So, can I say alternatives on this? How about creating schema objects in RDBMS? It is very useful for database administrators or newbies.