added "sign with GPG" step to the release stage in pom.xml
added "sign with GPG" step to the release stage in pom.xml

sleroy/redmine-java-api,redminenb/redmine-java-api,taskadapter/redmine-java-api,redminenb/redmine-java-api,taskadapter/redmine-java-api,Wurmy/My_Redmine-Java-API_XML,sleroy/redmine-java-api,stephenc/redmine-java-api