Implemented the SwaggerUI urls config parameter which displays a specs dropdown

[jvpernis]

When the urls parameter is specified in the SwaggerUI config, a dropdown of API specs is displayed instead of an editable textbox. This can greatly help organize the multiple specs in a project, as suggested in this StackOverflow answer.

This behavior is currently triggered by simply adding a name parameter to the specs object, e.g.:

{
    "specs": [
        {
            "version": "0.0.1",
            "title": "Api v1",
            "name": "v1",
            "endpoint": "v1_spec",
            "description": "This is the version 1 of our API"
        }
    ]
}

When this parameter is not included in the specs object, the editable textbox is displayed as usual. It might be more intuitive to have this behavior triggered by an external flag or something, but I'm not sure how this interface would look like.

Let me know if you have any ideas for this!

[deepak18]

@rochacbruno Do you plan to have a new release for the flasgger package anytime soon? Seems like it's been over a year since the last one and there have been some good features merged.