Bug 8773 - Start per-instance koha-index-daemon in .deb setup

Bug 8773 - Start per-instance koha-index-daemon in .deb setup

Short:

Launch an indexing daemon (rebuild_zebra.pl -daemon) process for each
enabled instance. Enabling/disabling the use of the indexer is handled
by global configuration variables in /etc/default/koha-common.

Also provides command line tools to manage the running indexer daemons
for your instances.

Long:

Using an indexing daemon avoids launching a new interpreter each time
the cron triggers the indexing, and also allows sub-minute incremental
reindexing, a requirement from our librarians.[1]

Using the indexer daemon could remain "experimental" until it gets more
testing; so is disabled by default initially. To enable the use of the
indexer the user has to tweak the /etc/default/koha-common config file.
Specifically the USE_INDEXER_DAEMON variable, which is clearly explained
in the file.

Frecquency defaults to 5 sec, and can be changed by tweaking the
/etc/default/koha-common config file too.

This patch uses rebuild_zebra.pl in daemon mode, but it is crafted to
allow changing the indexing daemon and passing specific option switches
it might need.

Regards
To+

[1] This is the .deb version of http://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=8519

Sponsored-by: Universidad Nacional de Cordoba
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>
Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Tomas Cohen Arazi <tomascohen@gmail.com>