Improve formatting for digital surrogates

[ahankinson]

Formatting and linking for digital surrogates is currently inconsistent. Some links include the 'note' field, while others don't, e.g.,

<ref><title></title><note></note></ref>

and

<ref><title></title></ref><note></note>

A minor style issue, but probably something where we can decide on a style and then fix whenever we see it.

[holfordm]

Most examples are of type 1, which also looks better when displayed (I think), so I say we go with that.