Refactoring of IBDNS.Name

Address some latent issues with the code handling domain names:

• details on how to convert relative to absolute names leak outside the module and live in the parser code, where it isn’t the best place;
• introduce the concept of relative vs. absolute names: the parser uses this heavily, and the Catalog’s nearest ancestor lookup function could benefit from it as well;
• implement the Inspect protocol so that domain names in logs show up in a nicer way;
• deprecate conversions from and to charlists, because we don’t need it anymore thanks to our migration to dns_erlang (see #17 (closed)).