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 believe that ```tajo_dump``` approach is productive to us in terms of development and more safe for upgrading. 

With ```tajo_dump```, the instruction of Tajo migration is as follows:

 1. execute ```tajo_dump``` to dump your all catalog information to **Tajo DDL statements** as a plan text file (e.g., backup.sql).
 2. create new database in your catalog store (PostgreSQL or MySQL) for migration
 3. change the catalog store config in ```catalog-site.xml``` in order to use newly created database
 4. restart a Tajo cluster 
 5. run ```tsql -f backup.sql``` to execute a sequence of **Tajo DDL statements** from the backup.sql

This approach naturally allows users to keep original catalog tables without additional database backup. Even if upgrade is failed, the original catalogs would be safe. 

Another motivation of ```tajo-dump``` approach allows us to change catalog schemas without considering schema upgrades. Actually, our catalog is still evolving rapidly. It may be important to us in this time.

This is my opinion. I'm open to any discussion.

Thank you for your work.