`Adaptable` provides the logic necessary for generic configuration of named adapter
configurations (such as the ones used in `Cache`) as well as a unified method of locating and
obtaining an instance to a specified adapter.
All immediate subclasses to `Adaptable` must define the protected attributes `$_configurations`
and `$_adapters`. The former is where all local adapter named configurations will be
stored (as an array of named configuration settings), and the latter must contain the
`Libraries::locate()`-compatible path string (or array of strings) specifying how adapter classes
should be located.
This static class should **never** be called explicitly.