Feature/support array queries

Now the same key could be defined in different files of the hierarchy, and the result will be the aggregated of all of them.

:hierarchy:
  - services
  - common

services.sql 
checks: SELECT type_name,title,command_line from checks where service='common';

common.sql 
checks: SELECT type_name,title,command_line from checks where service='%{::service}';