Improves the Json response handling

Replaces Core\Listener\JsonViewModelListener with Core\Listener\EnforceJsonResponseListener
which does the same but additionally checks for a route parameter names "forceJson" which when set
to true forces the use of a \Zend\View\Model\JsonModel.
It will transfer all variables from the old model to the new JsonModel.
In case of a dispatch error event, the message variable is transferred, and if display_exception is set,
the exception message is stored in the models' exception variable.
[Auth] Users can log in via an external application and RESTful requests.

* Creates an authentification adapter for external application authentification
* Creates a filter class for an user credential
* Creates a factory for the authentification adapter (mainly injects the user repository).
* Creates a new Listener "TokenListener" which listens on the Applications' bootstrap
  event at a very hight priority (to ensure it will be fired first)
  to automaticall fetches post or query tokens and set the session_id.

* Adds some module specific configuration in module.config.php
* Adds new Route "/login/extern"
* Adds new Controller Plugin in Core: Config
  Retrieves Module specific configuration from the big applications config array.

* Adds the "forceJson" route parameter to "login/extern"
* Adds new action "login-extern" to Auth\IndexController to handle login calls.
* Adds some methods to the user entity, (setCredential, setPassword, getCredential)
  setPassword is used to set a plain text password, which is then internally filtered to a
  credential string and set using setCredential.
  This is to avoid double filtering the credential upon retrieving an user from persistance.

* Attach the TokenListener in the modules init method to the shared event manager as this is
  the only way to connect to the bootstrap event that early.

* Fix: UserRepository uses wrong Hydrator class.

(#4344)