Support for RFC 7950

[scottwn]

It would be useful to support the features defined in RFC 7950, particularly the "action" statement. My team is using "action" to define certain operations. Currently we are duplicating this with an RPC in order to generate the swagger, but it would be better to be able to use "action" as intended.

[bartoszm]

Hi, @scottwn as you have probably noticed I have only a little time to work on the yang2swagger thus I am not sure whether I will be able to drive this development. Having said if you are interested in contributing something along this like I will be more than happy to carve out some time to support you.