BUG 2970 : Create a PruningDataTreeModification

BUG 2970 : Create a PruningDataTreeModification

The PruningDataTreeModification automatically tries to prune the passed
in NormalizedNode if an IllegalArgumentException is thrown when doing
a write or a merge on the DataTreeModification.

*I know* that doing the pruning on IllegalArgumentException is flaky but
that is the best I can do unless we can change the implementation in yangtools
to throw a more specific exception when the data node does not map to a
the schema context

Change-Id: Iea0cea82eda8bd51c1f3f07b063404458798c348
Signed-off-by: Moiz Raja <moraja@cisco.com>