Refactor the person table

It appears that the author specifications in some git commits are more free form than name <email>:

• some omit the name and keep the space ( <email>)
• some omit the name and the space (<email>)
• some have trailing spaces (name <email> )

I believe our way out is adding a fullname field to the person table, and making the name and email field "secondary" fields that are filled if we were able to parse the fullname.

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Migrated from T366 (view on Phabricator)