closes #805

In order to make the starters compliant to the spring boot naming rules
I added a codecentric-* prefix to the server and the client starters.
All samples are now using our starters and the docs were alignes with
these changes. In order to not suprise existing users I've added a
relocation to our old module

I removed the unecessary plugins from the build and reworked it to use
the ci friendly way of setting the version for releases (see
https://maven.apache.org/maven-ci-friendly.html).

With this commit you can specify either a URL or a serviceId for the
Turbine server location.
Note that `spring.boot.admin.turbin.url` is replaced by
`spring.boot.admin.turbine.location`.

closes #373

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 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

With this commit the support for Turbine is completly revised. From now
on Turbine is supported via a separate module and is integrated as top
level view.

closes #306

closes #299