Checks the DiscoveryClient's services on each heartbeat and removes all
services, which are no longer registered.

fixes #214

fixes #205

Use the metadata for health-/managament-url in the default service conversion.
This allows custom health- and management-path per application.

fixes #205

fixes #205

fixes #209

closes #201

fixes #202

From Spring Cloud Brixton on, the PreDecorationFilter doesn't pass sensitive
headers downstream.
So the ZuulProperties from the ApplicationContext needs to be used (instead
of creating a new instance), so that the properties can be customized.

Update to Spring Cloud Brixton and add the concept of ServiceInstanceConverters.
A ServiceConverter is used to convert discovered ServiceInstances to
Applications. The old converter and one for Eureka is provided. It is also
possible to provide your own implementation.

closes #154

fixes #184

fixes #175

added CompositeNotifier to allow for multiple notifiers. Only used when multiple notifiers are configured and no primary notifier is already configured.

Chrome dosesn't send parallel requests for the same url. To circumvent that
behavior add a dummy request-parameter to the event-stream url. Otherwise
the journal section shows no content on chrome while doing the sse long polling

Fixed HipchatNotifierConfiguration to be a static class

changed HipchatNotifierConfiguration to be a static class, otherwise application context doesn't start up when hipchat notification is enabled.

If the management.port and server.port is not the same, the current logfile-
endpoint detection fails. With this commit the presence of the endpoint is
determined via a HEAD-request

fixes #165

This commit contains multiple changes:
 - Start the registration task after the ApplicationReady event. This makes
   AdminClientProperties.isReady() unnecessary.
 - The RegistarApplicationListener has two new public methods to start/stop the
   periodic registration task.
 - Add spring.boot.admin.auto-registration property (default: true). When this
   property is set the registration task is automatically scheduled after the
   ApplicationReadyEvent.

closes #151