[proposal] Cache item : set lifetime of an item

This PR add the possibility to set a time to live **per item**.

It's not perfect : 
- there is a BC break in `/Zend/Cache/Storage/StorageInterface::setItem` prototype
- not all adapters can use this parameter

What to you think of it ?

Usecase : i needed to set a ttl for a doctrine result cache using [DoctrineModule/Cache/ZendStorageCache](https://github.com/doctrine/DoctrineModule/blob/master/src/DoctrineModule/Cache/ZendStorageCache.php#L75) with a memcached adapter