Tyk middleware to allow both Bearer-token and (signed) Cookie JWTs

This middleware is to allow both Authorization: Bearer-header and (signed) cookies in JWT-format to pass through the Tyk API Gateway.

The middleware will in practice:

1. Look for the COOKIE_NAME (access_token) in the cookies
2. Strip any signed parts of the jwt-cookie since TYK does not understand this.
3. Copy the JWT to HEADER_NAME (Authorization) with the HEADER_PREFIX (Bearer)

The middleware will not strip away the original cookie and does not remove the Authorization-header when done (this could be added in a "post-middleware" if required).