Create bi-directional schema version adapters

[mwatts15]

To support the use of data in a forward and backward-compatible manner, we can employ "schema version adapters" to translate between different versions of a schema. Such adapters would work at the point where they are needed in code in order to make data generated at a later date accessible to code created at an earlier date while still allowing the newer data to follow the structure of the most recent version. Such a scheme would need, in general, at least m-1 adapters for m versions since adapters could be chained. More adapters could be created for non-adjacent version numbers for efficiency or to preserve fields that were lost in an intermediate version.