SLING-3104 : ensuring proper (ie valid) java package name is generated out of groupdId/artifactId (while the user doesn't type anything in the java package field him/her-self

git-svn-id: https://svn.apache.org/repos/asf/sling/branches/tooling-ide-vlt@1526896 13f79535-47bb-0310-9956-ffa450edef68