serialize references separate from children

[dylangrandmont]

Not a tremendous fan of the approach but we'll need to separate the regular serialized content (children) and the reference content. This is required because templates can insert content, followed by a templated section (e.g. a signoff section), followed finally by references. This approach duplicates the children serialization in a minimal way to achieve this separation.

Opening for feedback

[dylangrandmont]

Closing in favour of a different implementation