SQL KeyValueStore

Change-Id: I8214a03cab65479dd7accfc8165b60ed195292a7
Reviewed-on: http://naan.mimuw.edu.pl:8001/87
Tested-by: Nebulostore Nebulostore <nebulostore@gmail.com>
Reviewed-by: Szymon Matejczyk <smatejczyk@gmail.com>