There is still now way to access what the flags mean, and the times
need to be in pure timestamp form, rather than erlang's.
Non-essential fields are allowed to be 'undefined' and then the
entry's field will remain zeroed.
This means we no longer accept any iolist in some of the functions,
but we might bring it back later.
There is also a new function, geef_ref:create_symbolic() to create
symbolic references, since we can no longer differentiate between a
name and an OID.
