feat(forms): add easy way to switch between forms modules (#9202)

modules/@angular/forms/src/forms.ts

@@ -0,0 +1,37 @@
+/**
+ * @module
+ * @description
+ * This module is used for handling user input, by defining and building a {@link FormGroup} that
+ * consists of
+ * {@link FormControl} objects, and mapping them onto the DOM. {@link FormControl} objects can then
+ * be used
+ * to read information
+ * from the form DOM elements.
+ *
+ * Forms providers are not included in default providers; you must import these providers
+ * explicitly.
+ */
+
+
+export {FORM_DIRECTIVES, REACTIVE_FORM_DIRECTIVES, RadioButtonState} from './directives';
+export {AbstractControlDirective} from './directives/abstract_control_directive';
+export {CheckboxControlValueAccessor} from './directives/checkbox_value_accessor';
+export {ControlContainer} from './directives/control_container';
+export {ControlValueAccessor, NG_VALUE_ACCESSOR} from './directives/control_value_accessor';
+export {DefaultValueAccessor} from './directives/default_value_accessor';
+export {Form} from './directives/form_interface';
+export {NgControl} from './directives/ng_control';
+export {NgControlStatus} from './directives/ng_control_status';
+export {NgForm} from './directives/ng_form';
+export {NgModel} from './directives/ng_model';
+export {NgModelGroup} from './directives/ng_model_group';
+export {FormControlDirective} from './directives/reactive_directives/form_control_directive';
+export {FormControlName} from './directives/reactive_directives/form_control_name';
+export {FormGroupDirective} from './directives/reactive_directives/form_group_directive';
+export {FormGroupName} from './directives/reactive_directives/form_group_name';
+export {NgSelectOption, SelectControlValueAccessor} from './directives/select_control_value_accessor';
+export {MaxLengthValidator, MinLengthValidator, PatternValidator, RequiredValidator, Validator} from './directives/validators';
+export {FormBuilder} from './form_builder';
+export {AbstractControl, FormArray, FormControl, FormGroup} from './model';
+export {NG_ASYNC_VALIDATORS, NG_VALIDATORS, Validators} from './validators';
+export * from './form_providers';