Bug 1292: Fix for NPE after notification get.

Fixed incorrect pass of SchemaContext in toNotification method in NetconfMessageTransformer class.
Added test for proper testing of resolving of notficiation message.
Added test models and test notification xml payload for testing purposes.

Change-Id: I4ada2fdf976003f4a2809d6cef53816ec39be364
Signed-off-by: Lukas Sedlak <lsedlak@cisco.com>
Merge "Bug 1292: Fix for NPE after notification get."