fix jar names

The build was creating jars with names like:

./grails-aether/build/libs/grails-aether-aether-2.3.0.BUILD-SNAPSHOT-javadoc.jar
./grails-aether/build/libs/grails-aether-aether-2.3.0.BUILD-SNAPSHOT-sources.jar
./grails-bootstrap/build/libs/grails-bootstrap-bootstrap-2.3.0.BUILD-SNAPSHOT-javadoc.jar
./grails-bootstrap/build/libs/grails-bootstrap-bootstrap-2.3.0.BUILD-SNAPSHOT-sources.jar
./grails-core/build/libs/grails-core-core-2.3.0.BUILD-SNAPSHOT-javadoc.jar
./grails-core/build/libs/grails-core-core-2.3.0.BUILD-SNAPSHOT-sources.jar

etc...