Small improvements to zlist

- improved some method documentation
- zlist_dup now copies autofree property as well
Trivial code cleanups
Removed empty ChangeLog
Updated man pages
Was missing API export for zhash_unpack
Clarified zlist manpage
Renamed zuuid_cpy to zuuid_export for clarity
Added access to uuid binary value
Added zuuid_dup method
Merge pull request #304 from hintjens/master

Minor project cleanups