Renamed namespace to JacobKiers
Renamed DataStore to DataStoreInterface

Also, the Interface now contains comments on the expected return values.
Added RequestInterface to make integration easier.

Since now only a RequestInterface is needed instead of a Request object,
it becomes easier to use the Server component with a different Request
object, such as the Symfony or Zend Framework Request objects.

This will now only need a small wrapper, instead of extending and
rewriting the existing Request object.