Automatically generate OSGi Manifest.mf and export all packages in addonX-api

The Forge APIs (org.jboss.forge.addon:resources-api, etc) should (as a part of the build process) automatically generate an OSGi Manifest.mf file to mark all packages provided by the API as exported.

The benefit of this is that consumers in an OSGi environment will automatically export necessary addon packages/types to dependent bundles without needing to explicitly do so in their manifest. (This should prevent common bugs with OSGi exports.)