typescript-node: Fix cookie auth, fix multiple API key auth

Created by: janjongboom

PR checklist

• Read the contribution guidelines.
• Ran the shell script under ./bin/ to update Petstore sample so that CIs can verify the change. (For instance, only need to run ./bin/{LANG}-petstore.sh, ./bin/openapi3/{LANG}-petstore.sh if updating the {LANG} (e.g. php, ruby, python, etc) code generator or {LANG} client's mustache templates). Windows batch files can be found in .\bin\windows\. If contributing template-only or documentation-only changes which will change sample output, be sure to build the project first.
• Filed the PR against the correct branch: master, 4.1.x, 5.0.x. Default: master.
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TC: @TiFu @taxpon @sebastianhaas @kenisteward @Vrolijkx @macjohnny @nicokoenig (2018/09) @topce @akehir

Description of the PR

This pull request fixes two issues with the typescript-node generator:

1. If multiple API Key authentication schemas are defined the generator emits code that won't compile.
2. in: cookie is not supported.

Multiple API Key authentication schemas

If you have the following OpenAPI definition:

components:
    securitySchemes:
        ApiKeyAuthentication:
            type: apiKey
            in: header
            name: x-api-key
        JWTAuthentication:
            type: apiKey
            in: cookie
            name: jwt

The generator emits the following code:

import { ApiKeyAuth } from '../model/models';		
import { ApiKeyAuth } from '../model/models';		

This won't compile. In api-single.mustache there's currently a loop around all authentication methods that outputs a single line depending on the authentication mode. This is not necessary as HttpBasicAuth, ApiKeyAuth and OAuth are always present in ../models/models. Always emitting a single line that references all of these will prevent this error.

in: cookie

components:
    securitySchemes:
        JWTAuthentication:
            type: apiKey
            in: cookie
            name: jwt

Will emit code that adds the API key to the query string, as in: cookie is not handled at all. This patch adds a handler that sets the Cookie header if this field is present.