Introduce a new base module

[bal-e]

This introduces a new_base module as a potential candidate for replacing base. While it has a similar structure (although much is left to be filled out), it has three distinguishing features:

1. It builds the foundation for a derive-based interface for easily and efficiently parsing (and possibly building) DNS messages.

2. It introduces RevName, a more efficient type for domain names (where labels are stored in reverse order).

3. It relies on the zerocopy crate to offload basic byte parsing, and to represent big-endian integers where necessary. This saves a fair amount of parsing code.

There's a lot more work to be done:

• Define some record data types (probably those from RFC1035).
• Define the OPT record data, and some EDNS option types.
• Define some common message structures (including a generic fallback).
• Update existing parts of the codebase to show the PR's benefits.
  • The client transports (... while remaining compatible?).
  • The stub resolver.
• Try defining some derive macros for the parsing/building traits.