[PATCH] Add default configuration values to the man page

[David Bremner]

Sergei Shilovsky <sshilovsky at gmail.com> writes:

>      **new.tags**
>          A list of tags that will be added to all messages incorporated
>          by **notmuch new**.
>  
> +        Default: ``unread;inbox``.
> +

There is actually something a bit subtle about some of these defaults.
Some of them are applied only to newly created configuration files,
while others are applied if there is now config value in the file.