Bug 6193 - Use memcached cache koha-conf.xml configuration variables

Bug 6193 - Use memcached cache koha-conf.xml configuration variables

Basically I add some code to Context.pm so it stores koha-conf.xml config vars
in memcached server. It is arguable whether this is an improvement or not,
tests are needed to conclude something about this.

Error handling was an issue with Cache::Memcached, I tried to do it the
simplest I could.

Note: As it was pointless to read the xml file to get the memcached
server info for accessing them for retreiving the info in the koha-conf.xml
file... I passed those values through apache's SetEnv. These variables
are set acordingly through the install scripts and commented out if koha
was setup not to use it.

Bug 6193 - Properly comment the code

Required by slef.

Regards
To+

Signed-off-by: Federico Rinaudo <frinaudo@infocpt.com.ar>
Signed-off-by: MJ Ray <mjr@phonecoop.coop>
Signed-off-by: Paul Poulain <paul.poulain@biblibre.com>
(cherry picked from commit 22dca58cbad64841fb12a6e48afa50500c1a5c60)

Signed-off-by: Chris Nighswonger <chris.nighswonger@gmail.com>