fix(ngSwitch): don't leak when destroyed while not attached

The leak can occur when ngSwich is used inside ngRepeat or any other
directive which is destroyed while its transcluded content (which
includes ngSwitch) is not attached to the DOM.

Refactor ngSwitch to use controller instead of storing data on compile
node. This means that we don't need to clean up the jq data cache.
Controller reference is released when the linking fn is released.

Closes #1621

test/ng/directive/ngSwitchSpec.js

@@ -90,4 +90,19 @@ describe('ngSwitch', function() {
     expect(child2).toBeDefined();
     expect(child2).not.toBe(child1);
   }));
+
+
+  it('should not leak jq data when compiled but not attached to parent when parent is destroyed',
+      inject(function($rootScope, $compile) {
+    element = $compile(
+      '<div ng-repeat="i in []">' +
+        '<ng-switch on="url">' +
+          '<div ng-switch-when="a">{{name}}</div>' +
+        '</ng-switch>' +
+      '</div>')($rootScope);
+    $rootScope.$apply();
+
+    // element now contains only empty repeater. this element is dealocated by local afterEach.
+    // afterwards a global afterEach will check for leaks in jq data cache object
+  }));
 });