Inconsistencies in Section 5 contracts vs examples

• Section 5 is somewhat inconsistent – the Lobby contract defines bindings as a list of str, but in the examples later in Sections 5.5.2 and 5.5.4 it describes the bindings as a list of uri.

Brian F made a comment in OBIX-212 about our original plan to use URIs for the encodings. We've changed those to str, but we need to revisit this section to make sure it is fully self-consistent.

Note the choice of of the of= value for the lists is somewhat dependent on issue OBIX-223 because, if we restrict ourselves from using complex structures according to the SHOULD rules in 9.3, then we'd have to use refs, or choose a different way to handle versioning.