[TypeScript] Convert directives (#396)

* Convert directives to TypeScript.

* FormDirective uses ValidationService type.

src/popup/app/directives/form.directive.ts

@@ -0,0 +1,31 @@
+import { ValidationService } from '../services/validation.service';
+
+export function FormDirective($rootScope: ng.IRootScopeService, validationService: ValidationService) {
+    return {
+        require: 'form',
+        restrict: 'A',
+        link: (scope: ng.IScope, element: ng.IAugmentedJQuery, attrs: ng.IAttributes,
+               formCtrl: ng.IFormController) => {
+            const watchPromise = attrs.bitForm || null;
+            if (watchPromise) {
+                scope.$watch(watchPromise, formSubmitted.bind(null, formCtrl, scope));
+            }
+        },
+    };
+
+    function formSubmitted(form: any, scope: ng.IScope, promise: any) {
+        if (!promise || !promise.then) {
+            return;
+        }
+
+        // start loading
+        form.$loading = true;
+
+        promise.then((response: any) => {
+            form.$loading = false;
+        }, (reason: any) => {
+            form.$loading = false;
+            validationService.showError(reason);
+        });
+    }
+}