The XCache adapter is meant to be used through the `Cache` interface,
which abstracts away key generation, adapter instantiation and filter
implementation.

A simple configuration of this adapter can be accomplished in `config/bootstrap/cache.php`
as follows:

{{{
use lithium\storage\Cache;

Cache::config(array(
    'cache-config-name' => array(
        'adapter' => 'XCache',
        'username' => 'user',
        'password' => 'pass'
    )
));
}}}

Note that the `username` and `password` configuration fields are only required if
you wish to use `XCache::clear()` - all other methods do not require XCache administrator
credentials.

This XCache adapter provides basic support for `write`, `read`, `delete`
and `clear` cache functionality, as well as allowing the first four
methods to be filtered as per the Lithium filtering system.

This adapter does *not* allow multi-key operations for any methods.