Bug 7286: rebuild_zebra_sliced for biblios and authorities

Bug 7286: rebuild_zebra_sliced for biblios and authorities

Complete rewrite of rebuild_zebra_sliced.zsh (renamed to .sh). Main
improvements are:
  - both biblio and authority records are handled
  - records are exported only once

It also add an option --skip-index to rebuild_zebra.pl that permit to
use rebuild_zebra.pl as an 'export only' script.

Description:
Index Koha records by chunks. It is useful when some record causes
errors and stop the indexation process. With this script, if indexation
of one chunk fails, chunk is splitted in 2 (or 3) chunks, and
indexation continue on these chunks.
rebuild_zebra.pl is called only once to export records.
Splitting and indexing is handled by this script (using yaz-marcdump and
zebraidx).

Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>