Added documentation and a sample on how to secure the SBA-Server and
leverage the new login ui-module

closes #361

This new ui-module provides a login page and a logout button.

closes #361

With this change it is possible to include credentials in the instance
metadata which will then be used to access the client endpoints using
HTTP Basic authorization.

closes #359

With this commit you can now associate your applications with custom
metadata using `spring.boot.admin.client.metadata.*` sensitive values
are recognized by key and are masked in the http interface.

This can be useful in the future if there are instance specific settings
which should be used by the admin server, e.g. custom notification
recipients.

For now there is no extra imetadata view in the ui. The values are shown
in the environment view.

* Number of concurrent requests for fetching the application info is
  limited to 15 requests

* Fetching the application info is deferred by 50ms to let the browser
  render the view

* Flattened application/group structure to save inner ng-repeat

* ng-repeat for notification settings and view drop down is executed
  when the popup/dropdown is visible

closes #348

When the list contains a lots of applications many requests are made for
dynamic views (e.g. heapdump, flyway, logfile, ...). With this commit
the availability check for these views is deferred until the user opens
toggles the dropdown. This should lead to far fewer requests.

fixes #346

Additionally the url list is not anymore overlapped then having a lot of
tabs for the detail views.

fixes #347

fixes #341

From this commit on the source from wich the application was registered
is remembered. We use this information for two things:
 * For applications which wasn't registered via the http-api the remove
   button is hidden.
 * The `ApplicationDiscoveryListener` only removes stale applications
   (those which are not anymore found via discovery) if the were registered
   via the `ApplicationDiscoeryListener`.

closes #328

With this commit the concept of an ApplicationFactory is introduced.
This allows you to easily modify the information used to register
your application at the admin server

closes #331

Since the logging backands may have different possible levels, we use
the list provided by the /logging endpoint

When hovering over the status a summary of the health indicators pops up
in application list and journal.

closes #334

The StatusInfo has a new details field. The StatusUpdater puts either the
reponse from the health endpoint or the exception message in the details.
This allows us to see the details over time (via the journal) and also to
use `em in a bit more mail notifications.

closes #329

The managment.ssl.* properties needs to be taken into account when they
are explicitly set and the managment.port differs from server.port

fixes #333

With this commits the server no longer depends on the client. The
classes for the clients are moved to de.codecentric.boot.admin.client
package.
Since the perspective on applications is totally different from client
and server the model has been split apart.

What means this for users:
1) The client is no longer a transitive dependency for your admin server
you may need to add it explicitly to your dependencies, respectively
jolokia-core in case you're using discovery and want to use the jmx-bean
interface

2)In case you have cutomised parts of the client you need to reflect the
package change.

fixes #332

Add support for the /loggers endpoint from spring boot 1.5.x. With this
change log4j2 (and every other logging backend supported by spring boot)
is supported in the logging view.
The old implementation will be kept a while, so that the clients aren't
forced to migrate.

closes #305

fixes #317

closes #323

closes #321

Display the version for groups. For multiple versions the lowest (by
lexical compare) gets chosen and a ellipsis is appended.

closes #312

Change the application list to a fixed table layout to prevent it from
overflowing in the window and limit the info column to a max width.
Also limit the info column in the detail view.

fixes #316