Add additional Method that check whether a table is empty or not

Application Devleopers are using queryNumEntries API
implemented by "COUNT(*)" to check whether a table is empty or not.
COUNT(*)  has to process the entire table to compute the result.
But, "EXISTS" can stop after a single matching row has been found.
So, Using "EXISTS" is more faster than "COUNT(*)"
I added new API using "EXISTS" to check whether a table is empty or not

Change-Id: Idcc2633d0a5349c59f41e125cf34c9dc6622cdbe