move messages.properties into omod during packaging

currently this modules fails to load when installed in openmrs 1.9.x
copying message.properties to omod during package to maintain compatibility with openmrs 1.9.x, as discussed here : https://issues.openmrs.org/browse/TRUNK-3889?focusedCommentId=209053&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-209053