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

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

Adds an application view that displays a list of
Liquibase migrations as retrieved from the /liquibase Actuator
endpoint. The module is conditional on this endpoint being
available.

Adds an application view that displays a table of
Flyway migrations as retrieved from the /flyway Actuator
endpoint. The module is conditional on this endpoint being
available.

Fixes gh-206

fixes #209

closes #201

fixes #202

With this commit the icons from FontAwesome are used. To achive this the
webpack css-loader is used and the location for the module.css has slightly
changed.
Also I removed the ugly sidebar (what a short life) and added a slim navbar at
the top for the detail views.

This adds a new FilteringNotifier which can use filters to suppres certain
events from being notified of. Two filter implementation are provided, one
filtering by name and one by id. Additional when a FilteringNotifier bean is
present, the autoconfiguration creates a REST-controller to add and remove
filters at runtime.

 - Updated Angular to 1.5.3
 - Removed Angular UI Bootstrap, to make the Angular update possible without
   updating Bootstrap
 - Moved every view into its own module
 - Added concatenation of the module js and css assets to the webserver
 - Created directives/components for the various visual components and trimmed
   down the controllers
 - Removed unecessary ngRoute
 - Removed classpath section in details (it is included in environment)
 - Moved the counters and gauges to a separated metrics view
 - Added target="_blank" for the logfile
 - Added information about version, loaded ui modules to the about page
 - Extracted the activiti view to a separate maven artifact

With this commit it is now possible to add your own ui modules to the servers
classpath and they will show up in the ui.
Every module needs an "entry" script file in the classpath located under
`META-INF/spring-boot-admin-server-ui/<modulename>/module.js`.
The module is be implemented as angular module and needs to be added to
the global `uiModules` list.
The spring-boot-admin-server-ui-activiti module is a simple sample for
adding a application view but it is also possible to add main-views.
Please have a look at the events module in spring-boot-admin-server-ui/modules.

Please note that the internals of the ui can change anytime.

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

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

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

The RemindingNotifier sends periodic notifications using a delegate. It must be
added explicitly to the ApplicationContext

The polling in the UI is replaced with server side events. Status changes are
now reported immediately from the admin server to the UI.

Cause it was often requested, now the context-path for the admin server is
configurable. This allows to move the admin-ui and endpoints to other http-
paths than "/".
NOTE: I'd still advise not to add the admin to the application you want to
monitor.

Spring Cloud Brixton hasn't been released yet, so to get the Spring Boot Admin
release out. We downgrade to Spring Cloud Angel.SR3.

To not pollute the log with warnings when an app is offline log the exception with
debug when the application status already was offline before the check. So only the
first exception when the state changes to offline will be logged.

closes #125

To not accidentally expose senstive urls only expose whitelisted
management-endpoints via the zuul proxy filter.

Deriving from Spring Clouds ProxyRouteLocator has become too difficult. It would
have required to either set fixed ZuulProperties or providing a DiscoveryClient.
So we are shipping our own lean version of it. Since the PreDecorationFilter is tightly
coupled to the ProxyRouteLocator we also have to use our own stripped down version.

closes #123

Check if the status field is a String and don't propagate any Exception
from the StatusUpdater, so that the application don't fail like in #120