Bidirectional static LSPs

[italobusi]

It seems that the ietf-mpls-static-extended module has been removed from draft-ietf-mpls-static-yang-14 and as a consequence the bandwidth attribute has to be moved to the base model (see issue #272 )

What about bidirectional static LSPs?

I think it may be useful to keep this definition. If not always needed/required, it could be in another module (as in previous versions of the I-D) or in the base module with a feature