Added support for persistent connection for Memcached.

[dorantor]

Subj. Now it's possible to use persistent connections with \Memcached. Just have to declare in assets/config/cache.php:

        'persistent_id' => 'my_persistent_id',
        'options'       => [
                \Memcached::OPT_SERIALIZER      => \Memcached::SERIALIZER_IGBINARY,
                \Memcached::OPT_BINARY_PROTOCOL => true,
        ],

or

        'persistent_id' => '%memcached.persistent_id%',
        'options'       => '%memcached.options%',

if you want to define it in assets/parameters.php.

[dorantor]

Did some testing and fixed couple of issues.

[dorantor]

Awesome! So PHPixie is alive after all :)
Will there be a release with this changes?