Added several more HTML5 samples

src/site/samples/dnd/example/basics.dart

+import "dart:html" as i;class l{const l();}class m{final  name;const m(this.name);}class n{const n();}class o{var q; start(){var h=i.document.queryAll('#columns .column');for(var g in h){g.onDragStart.listen(s);g.onDragEnd.listen(t);g.onDragEnter.listen(u);g.onDragOver.listen(v);g.onDragLeave.listen(AB);g.onDrop.listen(BB);}} s( h){var g=h.target;g.classes.add('moving');q=g;h.dataTransfer.effectAllowed='move';h.dataTransfer.setData('text/html',g.innerHtml);} t( j){var g=j.target;g.classes.remove('moving');var k=i.document.queryAll('#columns .column');for(var h in k){h.classes.remove('over');}} u( g){var h=g.target;h.classes.add('over');} v( g){g.preventDefault();g.dataTransfer.dropEffect='move';} AB( g){var h=g.target;h.classes.remove('over');} BB( g){g.stopPropagation();var h=g.target;if(q!=h){q.innerHtml=h.innerHtml;h.innerHtml=g.dataTransfer.getData('text/html');}}} main(){var g=new o();g.start();}