Updating cluster RPC code making it work

Added XMLUtils to serialize and deserialize instance identifier objects and the values insides path arguments with proper object type. This code use Yangtools existing utility, but modify that code to make sure
right type is picked up. We can think of adding it directly in yang tools also and remove it from here
Added Preconditions check for pojos

Change-Id: Ieb73b4ee660d2e058d0a62952799fc6f39d4c6b5
Signed-off-by: Harman Singh <harmasin@cisco.com>