removing visplugin class dependency

* added method for fetching plugin visualizer

tools/cooja/java/se/sics/cooja/Plugin.java

@@ -26,23 +26,34 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * $Id: Plugin.java,v 1.2 2007/01/10 14:57:42 fros4943 Exp $
+ * $Id: Plugin.java,v 1.3 2008/12/16 15:07:14 fros4943 Exp $
  */
 
 package se.sics.cooja;
 
 import java.util.Collection;
+
+import javax.swing.JInternalFrame;
+
 import org.jdom.Element;
 
 /**
- * Main interface for a COOJA interaction plugin. The typical interaction plugin
- * is a visualization plugin, see abstract VisPlugin for more information.
+ * COOJA plugin. For graphical plugins, extend abstract class VisPlugin.
+ * A plugin should also use ClassDecription and PluginType.
  *
+ * @see se.sics.cooja.ClassDescription
+ * @see se.sics.cooja.PluginType
  * @see se.sics.cooja.VisPlugin
+ *
  * @author Fredrik Osterlind
  */
 public interface Plugin {
 
+  /**
+   * Graphical component of plugin (if any)
+   */
+  public JInternalFrame getGUI();
+
   /**
    * This method is called when an opened plugin is about to close.
    * It should release any resources such as registered observers or