Testing variant publishing

- update to latest relast version
- add versions plugin

build.gradle

 plugins {
+    id 'com.github.ben-manes.versions' version '0.42.0'
     id 'java-library'
     id 'application'
     id 'org.jastadd' version "${jastaddgradle_version}"

gradle.properties

-relast_version = 0.3.0-137
+relast_version = 0.4.0
 relast2uml_version = 0.3.7-59
 jupyter_version = 5.8.2
 assertj_version = 3.22.0
 grammar2uml_version = 0.2.1
-jastaddgradle_version = 1.14.5
+jastaddgradle_version = 1.14.5
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