memcached changes

[marc-mabe]

• implemented namespace support manually to not change Memcached::OPT_PREFIX_KEY on a shared memcached resource
• added Zend\Cache\Storage\Adapter\MemcachedResourceManager that handles memcached resources
  • an instance of it can be given as a storage option resource_manager else it will be auto-instantiated by MemcachedOptions
  • memcached configuration options will be directed into the resource menager
  • it will lazy load the memcached resource by sharing it over adapters
  • it supports to change resource options after instantiating a resource
• removed the default server configuration 127.0.0.1:11211
  • could result in a connection to a wrong server be simply forget configuring it
  • memcached as a local only server doesn't make sense because it's better to storare into memory directly in such cases ( like APC )
• support persistent connections persistent_id
• changed default weight to 0 ( defined by Memcached::addServer )

It should be backward compatible but some methods of MemcachedOptions marked deprecated:

• getMemcachedResource setMemcachedResource Please use the resource manager instead
• addServer Please use the resource manager instead
• getLibOption setLibOption Please use lib_options or the resource manager instead

Open for discussion ;)