[NFR] Increment/decrement values in memcache

[jokaorgua]

Need a increment/decrement methods in memcache class which should work with native increment/decrement methods of memcache server.

These method are needed for making counters. get/save value are not atomic as increment/decrement

[thecodeassassin]

when this is implemented we should also use php5-memcached instead of php5-memcache

[ghost]

Can this one be closed now?