Support for Mailbox and Group addresses

[akshaymankar]

The section 3.4 of the RFC 5322 specifies how to parse a full mailbox or group address. For example things like: "Joe Q. Public" <[email protected]> or A Group:Ed Jones <[email protected]>,[email protected],John <[email protected]>;. There can also be comments like:

A Group(Some people)
        :Chris Jones <c@(Chris's host.)public.example>,
            [email protected],
     John <[email protected]> (my dear friend); (the end of the group)

I believe most of the parsers for these lexical elements are already present in the code. It would be nice to either expose them and/or write more parsers to parse the mailbox and group.

I would be happy to contribute code/tests for this.