Adds root directive to vhost_header and vhost_ssl_header templates.

This change will result in there being a 'root' directive in both the
server block, and the location sub-block. This is a perfectly valid
configuration and avoids the possible issue of having a location
with no 'root' if it isn't explicitly set.

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From #142, I thought this was the most concise way to solve the 'no root' issue, another possibility would be to remove the root directive from the default '/' location, but having the duplicate has no ill-effects and keeps the '/' location consistent with any others added to the vhost.