Add access controls for Databases/Tables

Squashed commit of the following:

commit ac3c82b7e8d1fd7d2932a33ea17423e5bc8c37ae
Author: TAGOMORI Satoshi <tagomoris@gmail.com>
Date:   Fri Apr 4 20:35:36 2014 +0900

    add docs for access control

commit eeda7249a6af6794705cb510636f7282ad4cf79d
Author: TAGOMORI Satoshi <tagomoris@gmail.com>
Date:   Fri Apr 4 20:11:10 2014 +0900

    fix for variable scope

commit 438fa5b0da1ca72a744a21e0369772d84741b57c
Author: TAGOMORI Satoshi <tagomoris@gmail.com>
Date:   Fri Apr 4 19:47:36 2014 +0900

    add access controls to show databases/tables/partitions and execution of query