Adding "Interface" suffice to class names in order to match existing practices.

The existing standards end their interface names with "Interface", so
this has been updated to match that.
Removed duplicate interfaces

There were example interfaces that matched those in the proposal but
were separate to help with distribution. However, with the continued
changes being made the interface files outside of the actual proposal
have been been kept up to date.

Once the proposal is actuall finalized the interfaces will need to be
distributed, but that is most likely going to be under a different
repository.
Changed getItemIterator to getItems, as seems to be the current popular choice.

This may change based on mailing list conversations, but enough people
have made this request where I'm comfortable with it being the current
text.