Add URL permission for http requests

[henricazottes]

Follow up of #5242

What about adding a new permission --allow-url=<URL>?

For a moment I though about adding URL support to --allow-read and --allow-write because file URI and URLs are kinda close, but splitting permission for URLs doesn't really make sense. Thus adding a new --allow-url permission.

Features:

• handle wildcards for
  • subpath: foo.com/bar/*
  • subdomain: *.foo.com