2 files for diff json/yaml file

[xuweibj]

inventorydiff.py and structurediff.py for #108

In inventorydiff.py, load json/yaml file and convert to dict, call StructureDiff().diff(d1, d2, self.isall) in structurediff.py to get diff dict.

If needed, call StructureDiff().rept(diff_dict, self.fmt) to show difference as json/yaml format.

Several modules called but not in these files:

• mgr.export_by_type just for our product, please ignore.
• loadfile load json/yaml file to get dict data.
• filter_dict_keys if "key" of d1 or "key" of d1[key] not in d2, delete it

[seperman]

Thanks @xuweibj and your team for the contribution! Merging.