Introduction of XSQL

XSQL is SQL wrapper for MD-SAL Data Broker
which provides query capabilities for MD-SAL 

YANG model is rendered as set of virtual tables 
and where leafs are columns in that table.

For more information see

https://wiki.opendaylight.org/view/OpenDaylight_Controller:MD-SAL:XSQL

Change-Id: I9224c100ffe5e50559fc7181f1c9a79b3f7b2a32
Signed-off-by: Sharon Aicler <saichler@cisco.com>
Merge "Introduction of XSQL"