docker: use always latest Graphviz release

This will change the Graphviz behaviour inside the docker container.
Until now it was always a fixed Graphviz version inside the Dockerfile.
With these changes the docker container will always use the latest Graphviz release if the version was not manually set via the docker build argument `GRAPHVIZ_VERSION`.

If not set as build arg fetch latest version of Graphviz based on their release name by default.
An alternative would be to use `tag_name`.

Also, to avoid the overhead of getting all kinds of relase data, GitLabs GraphQL interface could be used.
```bash
curl -s \
  -H "Content-Type:application/json" \
  -d '{"query": "{project(fullPath:\"graphviz/graphviz\"){releases(first:5,sort:RELEASED_AT_DESC){nodes{name}}}}"}' \
  "https://gitlab.com/api/graphql" \
| jq -r '.data.project.releases.nodes[].name' | sort -V -r | head -n 1
```
In GraphQL the alternative to `name` would be `tagName`.

Dockerfile.jetty-alpine

@@ -25,16 +25,18 @@ RUN apk add --no-cache \
     /generate-jetty-start.sh
 
 #RUN apk add --no-cache graphviz
-ARG GRAPHVIZ_VERSION=8.0.2
+ARG GRAPHVIZ_VERSION
 ARG GRAPHVIZ_BUILD_DIR=/tmp/graphiz-build
 RUN apk add --no-cache \
         g++ \
+        jq \
         libexpat \
         make \
         zlib \
         && \
     mkdir -p $GRAPHVIZ_BUILD_DIR && \
     cd $GRAPHVIZ_BUILD_DIR && \
+    GRAPHVIZ_VERSION=${GRAPHVIZ_VERSION:-$(curl -s https://gitlab.com/api/v4/projects/4207231/releases/ | jq -r '.[] | .name' | sort -V -r | head -1)} && \
     curl -o graphviz.tar.gz https://gitlab.com/api/v4/projects/4207231/packages/generic/graphviz-releases/${GRAPHVIZ_VERSION}/graphviz-${GRAPHVIZ_VERSION}.tar.gz && \
     tar -xzf graphviz.tar.gz && \
     cd graphviz-$GRAPHVIZ_VERSION && \
@@ -43,6 +45,7 @@ RUN apk add --no-cache \
     make install && \
     apk del --no-cache \
         g++ \
+        jq \
         libexpat \
         make \
         zlib \