Add a .mailmap file that can be used via the mailmap functio in mercurial templates to map author names/email addresses.

Some of these aren't matching right yet, but at least we have the dupes now and don't have to search for them again.

Also, I did a lot of guess work here on proper emails and usually deferred to gmail over a custom domain.

Testing Done:
Lots of shell magic involving `hg log -T '{mailmap(author)}\n'` and without the `mailmap`.

Reviewed at https://reviews.imfreedom.org/r/875/