Add a compareNamespace utility

compareNamespace recursively compares 2 Namespace or dict
keys and subkeys, and returns a delta with added, removed,
changed and unchanged keys

filterDelta removes from the delta the parent keys to limit
the delta to the strict minimum

Signed-off-by: Olivier Monnier <olivier.monnier@intel.com>
Simplify and factorize compareNamespace utility

Signed-off-by: Olivier Monnier <olivier.monnier@intel.com>
Merge branch 'master' of https://github.com/omonnier/dictns

Conflicts:
	test/test_namespace.py