Allow per-path entries to be other things than maps

[richcarl]

The entries of a path are typically methods like "get": {...}
but can also be path-global things such as "parameters": [...]
Example:

    "/users/{id}": {
        "parameters": [
            { "in": "path",
              "name": "id",
              "required": "true",
              "type": "string",
              "description": "The user ID"
            }
        ],
        "get": {
            ...
        },
        "post": {
            ...
        }
    }

[elbrujohalcon]

Please merge from master to avoid CI issues.