Create Maven "lockfile" using built-in from maven.... It supports a dot, graphml and tgf output format. (And now JSON!)

- See also https://github.com/search?q=maven+dependency+tree&type=repositories
- Note that the `mvn dependency:tree` command would typically process all pom.xml in the codebase at once, and would generate one tree for each each pom.xml
- a good set of args to run the command would be : `mvn dependency:tree -DoutputFile=maven-dependency-tree.lock -DoutputType=graphml` and optionally with`-Dmaven.test.skip=true` and `-DskipTests` to skip tests, or various other options (such as scope) to filter the tree. See https://maven.apache.org/plugins/maven-dependency-plugin/tree-mojo.html
- See also https://github.com/jfrog/maven-dep-tree

Note that Maven now has a JSON format!
- https://github.com/apache/maven-dependency-plugin/pull/325
- then https://github.com/apache/maven-dependency-plugin/pull/391