Currently, writer registry only supports ordering on:

• root node level
• same level child nodes (thanks to composite writer structure)

This has to change. Ordering between child nodes on different levels must be supported as well as inter-subtree ordering.

Right now the registry is just a linked map for root writers. This has look more like a flat linked map for all the writers. This way ordering can be fully customized, no need for reflexive writers, but still extensible. The only issue is with writers handling also children nodes, for them, changes have to be aggregated and handled by the writer.