Bug 17332: Include memcached configuration in koha-conf files

Bug 17332: Include memcached configuration in koha-conf files

This patch introduces the memcached_servers and memcached_namespace
configuration entries as expected by 11921.

Note: better test this one and the followup together to ease the process.

To test:
- Do a source Koha install (dev, standard, single)
=> SUCCESS: The resulting koha-conf.xml file includes the memcached_* entries
   which are filled with the right values.
- In kohadevbox (packages setup):
- Replace /etc/koha/koha-conf-site.xml.in with the one from this patch
- Create a new koha instance
=> SUCCESS: The instance's koha-conf.xml includes the relevant entries
- Sign off

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>