More user-friendly allow/deny domain/IP block list format: allow end-of line comments, make IPs optional

[tredondo]

https://github.com/evilsocket/opensnitch/wiki/block-lists states the allow/block lists must be in hosts format, and:

Lines started with # are ignored. Write comments always on a new line, not after a domain.

This is good for compatibility, but cumbersome in practice:

• All domains must be prefixed by 0.0.0.0. That results in a lot of noise in the file.
• Comments can only be added on a standalone line. This makes sorting the file risky, because comments will be separated from their domains, unless you build a custom sort tool aware of this limitation.

Proposal

1. Allow end-of-line comments. # is not a valid domain character, so anything following \s*# can be safely ignored. This will keep comments attached to their domains:

   d1fc6k0zwgx3pa.cloudfront.net # Instacart CDN
   

2. Make the 0.0.0.0 IP part optional. In other words, if a string is standalone on the line, accept it as a domain, up to \s*(#.*)?$