docs(form): minor form doc and example fixes

Form documentation fixes:
- Fix broken form example in docs
- A few small other corrections in form docs.

src/ng/directive/form.js

@@ -14,13 +14,13 @@ var nullFormCtrl = {
  *
  * @property {boolean} $pristine True if user has not interacted with the form yet.
  * @property {boolean} $dirty True if user has already interacted with the form.
- * @property {boolean} $valid True if all of the containg forms and controls are valid.
+ * @property {boolean} $valid True if all of the containing forms and controls are valid.
  * @property {boolean} $invalid True if at least one containing control or form is invalid.
  *
  * @property {Object} $error Is an object hash, containing references to all invalid controls or
  *  forms, where:
  *
- *  - keys are validation tokens (error names) — such as `REQUIRED`, `URL` or `EMAIL`),
+ *  - keys are validation tokens (error names) — such as `required`, `url` or `email`),
  *  - values are arrays of controls or forms that are invalid with given error.
  *
  * @description
@@ -133,7 +133,7 @@ function FormController(element, attrs) {
  * does not allow nesting of form elements. It is useful to nest forms, for example if the validity of a
  * sub-group of controls needs to be determined.
  *
- * @param {string=} ngForm|name Name of the form. If specified, the form controller will be published into
+ * @param {string=} name|ngForm Name of the form. If specified, the form controller will be published into
  *                       related scope, under this name.
  *
  */
@@ -206,12 +206,12 @@ function FormController(element, attrs) {
        </script>
        <form name="myForm" ng-controller="Ctrl">
          userType: <input name="input" ng-model="userType" required>
-         <span class="error" ng-show="myForm.input.$error.REQUIRED">Required!</span><br>
+         <span class="error" ng-show="myForm.input.$error.required">Required!</span><br>
          <tt>userType = {{userType}}</tt><br>
          <tt>myForm.input.$valid = {{myForm.input.$valid}}</tt><br>
          <tt>myForm.input.$error = {{myForm.input.$error}}</tt><br>
          <tt>myForm.$valid = {{myForm.$valid}}</tt><br>
-         <tt>myForm.$error.REQUIRED = {{!!myForm.$error.REQUIRED}}</tt><br>
+         <tt>myForm.$error.required = {{!!myForm.$error.required}}</tt><br>
         </form>
       </doc:source>
       <doc:scenario>