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).

This removes the spring-boot-starter-parent from the build, and
duplicates the necessary plugin configuration in he Spring Boot Admin'
parent instead. This way our BOM doesn't include version for
dependencies managed by boot's BOM