This Package will contain YANG models for sonic which are written with guidelines mentioned in
https://github.com/Azure/SONiC/blob/master/doc/mgmt/SONiC_YANG_Model_Guidelines.md.

This package will include python yang libraries which will be used with sonic utilities
pacakge to validate the config.

      - python APIs based on libyang
      - functions to load/merge yang models and data files
      - add/set/delete node in schema and data trees
      - find dependencies

…, PortChannel and ACL.

[Sonic Yang Tree]: YANG models as per Guidelines.

Guideline doc: https://github.com/Azure/SONiC/blob/master/doc/mgmt/SONiC_YANG_Model_Guidelines.md

[yang-model-tests]: YANG model test code and JSON input for testing.

[setup.py]: Add testing for yang models.

[sonic-slave-stretch]: Add a package ijson for sonic_yang_mgmt build.

…ansalation, reverse translation of config DB.

This PR includes:
-- Cropping input config based on Yang Model.
-- Translate input config based on Yang Model.
-- rev Translate input config based on Yang Model.
-- Find xpath of port, portleaf and a yang list.
-- Find if node is key of a list while deletion if yes, then delete the parent.