fixes #477

With this commit all values from /metrics are shown and a option to
filter these values is provided

closes #264

Until now the thread querying the application endpoint can be blocked
for a very long time when the application is inresponsive. With this
commit two new properties `spring.boot.admin.monitor.read-timeout`
(default: 2s) and `spring.boot.admin.monitor.connect-timeout` (default:
5s) are added.

closes #462

Since the healthIndicator for Hystrix lists all discovered services, it
looks like the filtering is broken.  So we need to ignore the status
information when filtering the application list.

fixes #438

closes #439

Adds a workaround for
https://github.com/spring-cloud/spring-cloud-netflix/issues/1815
by including spring-cloud-context to the server's dependencies

A new property `spring.boot.admin.discovery.services` is added. It can
be used to restrict the services registered via discovery to a
whitelist (supporting simple patterns). Until now only blacklistin was
supported. The default whitelist permits all services.

Brings a fixed httpclient.

fixes #419

https://github.com/spring-cloud/spring-cloud-netflix/pull/1372 has been
merged. So it is save to remove the local workaround.

Adds an new Notifier implementation for Let's Chat.

The value from max memory isn't necessarily the -Xmx parameter,
therefore we remove the label

fixes #413

Since the Notifiers shouldn't throw exceptions, we let all extend the
AbstractEventNotifier which gets us a enabled property and catching
exceptions which may occur when notifiying.

To make custom NotifierConfigurations easier and less error prone we now
instantiate the Notifier Beans regardless of the corresponding enabled
property

closes #402

Posting via zuul doesnt work in case the Content-Type has a charset
specified.
Applied fix from spring-cloud/spring-cloud-netflix#1663

fixes #403

closes #404