Add Designer specific elements to JBoss Central

* org.teiid.designer.jboss.tools.central
 * Plugin extends the default configurator responsible for providing content
   to JBoss Central
 * Adds a link for the new model project wizard

* org.teiid.designer.jboss.tools.feature
 * Feature for plugins with dependencies on jboss tools plugins that may
   not be essential. We already need jboss.as plugins for the Server View
   but they are more necessary than the dependencies for this plugin.
 * Designer's jboss central plugin added to this feature

* org.teiid.designer.feature
 * Includes jboss.tools.feature as an optional inclusion so that if the
   dependencies are not satisfied then it is not installed.