feat: inject branch slug into SNAPSHOT version

mentioned in commit b166dd79

mentioned in merge request to-be-continuous/samples/maven-on-openshift!42 (closed)

mentioned in merge request to-be-continuous/samples/maven-on-gcloud!84 (merged)

mentioned in merge request to-be-continuous/samples/maven-on-kubernetes!95 (merged)

mentioned in merge request to-be-continuous/samples/maven-library!33 (merged)

mentioned in merge request to-be-continuous/samples/maven-on-kubernetes!97 (merged)

mentioned in merge request to-be-continuous/samples/maven-on-openshift!48 (merged)

mentioned in issue #58 (closed)