Support to add prefix and extra header to address field

[DhananjayPurohit]

There should be a parameter to include a prefix in the address field. Currently, adding a complete URL to the address results in a 502 Bad Gateway error. Additionally, a feature to include extra headers in the configuration should be supported.

The service configuration file (aperture.yaml) should look like this:

- name: "service1"
  hostregexp: "^localhost:8081$"
  pathregexp: '^/api$'
  address: "0.0.0.0:443"
  protocol: https
  header:
    Authorization: "Bearer key"
  price: 10
  rewrite:
    prefix: "/path/to/api"