HC2VPP-297 - MPLS model updates

HC2VPP-297 - MPLS model updates

This patch updates MPLS models to:
- [email protected]
  (draft at: https://tools.ietf.org/html/draft-ietf-mpls-static-yang-05)

Due to odl bugs these models were changed,
see HC2VPP-307 for more details.

see mpls_postman_collection.json for examples and usage

Summary of changes:
- leaf operation in static-lsp->config was replaced
  with mpls-operations-type
- paths were refactored and moved to static-lsp
- outgoing-labels container was introduced in
  static-lsp->paths
- MPLS docker demo was updated to reflect model changes

Change-Id: I725ec5e4b3a1acea2aeabec41185949fc498ff26
Signed-off-by: Michal Cmarada <[email protected]>