* feat(minecraft-server): add onbuild trigger
Added a ONBUILD trigger for the [ToF-BuildTools](https://git.faldoria.de/tof/server/build-tools).
If a plugins.yml is provided the BuildTools will download all plugins configured in the YAML.
https://github.com/itzg/dockerfiles/issues/218
* feat(minecraft-server): add arg for build output
* fix(minecraft-server): syntax error in Dockerfile
* fix(minecraft-server): chown jar files after building
* feat(minecraft-server): cleanup buildtools after using
* fix(minecraft-server): remove /plugins volume
The /plugins volume causes weird behaviour when prepolulating it with
files on build. Removing it as an explicit volume fixes that.
* mc: add example Dockerfile for ToF builds
* docs(minecraft-server): add docs for new onbuild trigger
* fix(minecraft-server): use correct url for build tools download
