Bug 10733: Memcached on package installs

Bug 10733: Memcached on package installs

This patch makes the koha-create script adjust the koha-conf.xml file
with the proper string substitutions to enable the use of memcached
for the created Koha instance.

It adds three option switches that control this:

 --use-memcached (defaults to "no")
 --memcached-servers "host1:port1,..." (defaults to '127.0.0.1:11211')
 --memcached-prefix "desired_namespace prefix" (defaults to 'koha_')

It respects the current schema configuration schema, where configuration
values are pondered like this:

hardcoded < koha-sites.conf < koha-create option switches

koha-sites.conf is read for USE_MEMCACHED, MEMCACHED_SERVERS and
MEMCACHED_PREFIX.

Note: the docs discourage setting user's own namespace prefix.

Using memcached is off as the default. The relevant configuration
variables will remain empty if the user doesn't pass --use-memcached
to the command. It matches the current behaviour.

To test:
- Apply the patch
- Build your own packages and install them on a test server
a) Create a new instance without using the new switches like:
 $ koha-create --create-db memctest
 - Check that /etc/koha/sites/memctest/koha-conf.xml contains:
   * Empty <memcached_servers> tag.
   * Empty <memcached_namespace> tag.

b) Play with the possible combination of option switches
(Note that the code defaults to empty and will remain like that if
--use-memcached is not used, so less tests...)

 $ koha-create --create-db --use-memcached memctest
 $ koha-create --create-db --use-memcached --memcached-servers "anything:xxx" memctest
 $ koha-create --create-db --use-memcached --memcached-servers "anything:xxx" --memcached-prefix "something" memctest
 $ koha-create --create-db --use-memcached --memcached-prefix "something" memctest

 - Check the koha-conf.xml and /etc/apache2/sites-enabled/memctest
   file reflect the chosen options.

c) Run
 $ koha-create --help
 - It should advertise this addition accordingly.

d) Run
 $ man koha-create
 - Man page for koha-create should provide good information on the new
   switches behaviour

Sponsored-by: Universidad Nacional de Cordoba
Signed-off-by: Mark Tompsett <mtompset@hotmail.com>
Signed-off-by: Robin Sheat <robin@catalyst.net.nz>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>