Infrastructure

Currently, the spec calls for for MNs to include serialization and deserialization support for XML, JSON, RDF, CSV, HTML AND TEXT (or LOG) formats for all types, including exceptions. We should consider removing them all, except for XML. Rationale: If there were only a few MNs planned to be in existence, and those were maintained and developed by DataONE, it would make sense to offer many serialization formats because it makes it easier to write clients. But because there will be many MNs, developed and maintained by many entities, I don't think the development effort involved in supporting all of the serialization formats for all of the MNs will be justified just for giving more choices for developers of clients. At the same time, if each MN does not support ALL serialization types, then clients will quickly be forced to use a "lowest common denominator" for which serialization format they chose, and that format will be XML.