Task: Apply the same shape to the curve configuration document

The curve configuration document gets the treatment the conventions document got. It stops being one value carrying every curve family, and the operations that write and read it stop reaching every family from one translation unit.

• The curve configuration document is split by family, and no type in refdata carries every curve family.
• The protocol and handler are split so that each translation unit reaches one family, following the measurement in Fix the tenor basis swap convention model and the document TU.
• The import applies the families as a bundle in one unit of work, as the conventions import does.
• The curve configuration document the ORE path writes and reads is the same document before and after, proven by importing and exporting a sample unchanged.

Follow the conventions half. Agree who owns the protocol split with the tenor basis swap story, then move the families off the document, then the protocol and handler, then the ORE path.

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• This ground is shared. The story Fix the tenor basis swap convention model and the document TU owns the task to split the configuration document protocol by family, and it covers the curve configuration half as well as the conventions half. Agree which environment holds the protocol split before either starts, or both will rewrite the same header.
• The curve configuration document is now the only document riding in configuration_document_handler.cpp. The conventions operations left that unit when the conventions import moved to the bundle, so the handler is a curve handler in all but its name.

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