Added support for parametric rewrite prefix

[VazeeKevin]

This PR adds support for parametric path with both prefix and rewritePrefix
Example:

// /rest-api/123/endpoint will be proxied to http://my-rest-api.example.com/123/endpoint
server.register(proxy, {
  upstream: 'http://my-rest-api.example.com',
  prefix: '/rest-api/:id/endpoint', // optional
  rewritePrefix: '/:id/endpoint', // optional
  http2: false // optional
})

Checklist

• run npm run test
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[mcollina]

lgtm