Code cleanup.

Removing usage of EDE_PANEL_APPLET_CLASS since there is no much usage of it. Also, marked all applet widgets as EDE_PANEL_WIDGET_TYPE so panel knows it is widget.

Added license info in some code, but whole ede2 tree needs to be revised for that.

ede-panel/applets/demo/AppletDemo.cpp

@@ -4,7 +4,7 @@
 #include <FL/Fl.H>
 #include <stdio.h>
 
-EDE_PANEL_APPLET_CLASS(MyButton, Fl_Button) {
+class MyButton : public Fl_Button {
 public:
 	MyButton() : Fl_Button(0, 0, 90, 25, "xxx") { 
 		color(FL_RED);