hibari >> gh33 (bad sequence) and gh34 (scavenger enhancements):
- Enhancements on the scavenging process:
  * the fun created by gmt_hlog_common:scavenge_one_seq_file_fun/1
    now handles unexpected errors so that scavenging process can
    continue on other seq files.
  * gmt_hlog_common:scavenger_move_hunks1/8 now try to continue moving
    live hunks even if some errors has been occurred.
  * gmt_hlog_common:scav_check_shutdown/1 now reports a summary of
    canceled scavenging process. (done by adding #scav_progress{}
    and scav_print_summary/2)  It now deletes work files too.
  * scavenger_commonlog_bottom/1 now skips to copy live hunks when
    is no such hunks

- A bug fix in write_hunk_bytes of gmt_hlog_local:
  * fix a potential bug in handle_call/3 for 'write_hunk_bytes' with
    'metadata', which causes to return a wrong offset. (The caller
    doesn't use the returned value so this bug had no actual impact)

- Refactoring hlog_common and brick_ets modules:
  * Rename type eee() in gmt_hlog.hrl to metadata_tuple()
  * Moved an expression to create a metadata_tuple() from
    gmt_hlog_local:handle_call/3 to make_metadata_tuple/7 for clarity
  * Add live_hunk_sizes field to #scav{} record
  * Add a type called scavenger_move_hunks_result
  * Add type do_mod() and some specs to brick_ets module.
  * Remove unused 'relocate_*' fields from #wb{} record in
    gmt_hlog_common module
  * Replace some "if" expressions with pattern matches

- Misc
  * gdss-brick >> GH9 (refactor #state{} record) - Add some comments
    to #state{} record in brick_ets.erl
  * Replace double-space with single-space in the @doc in
    gmt_hlog_local module.
  * Replace "GDSS" with "Hibari" in the @doc too.