The function to convert signatures into erlang terms was returning ok
with the rest of the tuple which geef_sig expects. We do not want the
ok there, so let that function give us the four terms and decide what to
do in each case.
The signature functions still want to return with ok before it, but the
reflog wants them together with the other parameters.
For now it simply includes reading in the reflog as a list of
entries. This does mean that the drop/append functions don't need to be
wrapped, as we can use erlang's list handling.
It however also means that we cannot write this back out, as there is
currently no way to create an empty reflog that we can fill with our own
list.
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.
This makes it useful for users of the bindings. The naming is the same
as the module to allow elixir to treat the records in much the same
way as its native module/record hybrid.
