ALTER TABLESPACE LOCATION support

Currently, Tajo uses tajo.warehouse.directory to a default tablespace. The default tablespace is stored to catalog server when TajoMaster starts up firstly.

Some users can change tajo.root after they use Tajo for a while. In this case, the mismatch between tajo.root and the default space can cause some problems. To avoid this confusion, we need to support ALTER TABLESPACE to change tablespace's URI.

The semantic is as follows:

ALTER TABLESPACE <space name> LOCATION '...';