DBRef encoding moved to Codecs.  This might not be the long term vision, since encoding and decoding is not symmetrical
Added CodeWithScopeCodec
Changed NoOpCodec to NoCodec, and have it throw an error if it is called.
Using the new CodeWithScopeCodec in the DocumentCodec; added tests to cover it.
Tidied up the encoding side of DocumentCodec
Changes to get the Pojo acceptance test running.  Works in IntelliJ but not the command line.
Removed now-redundant Datastore