Make clients opt in to decoding objects that are stored
in the generic api.List object by invoking runtime.DecodeList()
with a set of schemes. Makes it easier to handle unknown
schema objects because decoding is in the control of the code.
Add runtime.Unstructured, which is a simple in memory
representation of an external object.
Standardize how our fakes are used so that a test case can use a
simpler mechanism for providing large, complex data sets, as well
as represent queries over time.
