With this commit you can from now on register the application on multiple
servers. You need to set spring.boot.admin.register-once to false and
assign a list of urls to spring.boot.admin.url

fixes #230

fixes #226

Sometimes Eureka only provides only the securedhealthUrl for the service.
Previous to this commit the applciation won't be registered in that case. So
with this commit the securedHealthUrl from Eureka is used, when available

fixes #224

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.