Decouple the api gateway integration out from core repo

The CLI integration with API gateway is function that can be split into it's own repository.

I envision having a repo that contains the api integration i.e. `openwhisk-cli-apigateway`

This repo can contain the routemgt web actions, go code to implement the `$ wsk api` command, and any tests to validate that functionality of the integration is always healthy using CI Travis.

This can be the repo that tests the integration between the two component repos `openwhisk` and `openwhisk-apigateway`

Start by locating the routemgt web actions, the Go implementation of the `$ wsk api` command, and their tests in the core repository. Review how these pieces integrate with `openwhisk` and `openwhisk-apigateway`, then define the new `openwhisk-cli-apigateway` repository and Travis CI coverage for that integration. Done means the API gateway functionality and its tests no longer need to remain in the core repository.

Written by the indexing model from the issue text.