docs(ngModelController): update wordings, add more general info

The wordings in setDirty etc. were specific to inputs, but ngModelCtrl
is agnostic to this and the preferred term is 'control'. I also
added some more info about this to the description, and linked to
the example that now lives at the bottom of the page.

Author: Narretz

src/ng/directive/input.js

@@ -1618,12 +1618,15 @@ is set to `true`. The parse error is stored in `ngModel.$error.parse`.
  *
  * @description
  *
- * `NgModelController` provides API for the `ng-model` directive. The controller contains
- * services for data-binding, validation, CSS updates, and value formatting and parsing. It
- * purposefully does not contain any logic which deals with DOM rendering or listening to
- * DOM events. Such DOM related logic should be provided by other directives which make use of
- * `NgModelController` for data-binding.
- *
+ * `NgModelController` provides API for the {@link ngModel `ngModel`} directive.
+ * The controller contains services for data-binding, validation, CSS updates, and value formatting
+ * and parsing. It purposefully does not contain any logic which deals with DOM rendering or
+ * listening to DOM events.
+ * Such DOM related logic should be provided by other directives which make use of
+ * `NgModelController` for data-binding to control elements.
+ * Angular provides this DOM logic for most {@link input `input`} elements.
+ * At the end of this page you can find a {@link ngModel.NgModelController#custom-control-example
+ * custom control example} that uses `ngModelController` to bind to `contenteditable` elements.
  *
  * @example
  * ### Custom Control Example
@@ -1861,9 +1864,9 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
    * @description
    * Sets the control to its pristine state.
    *
-   * This method can be called to remove the 'ng-dirty' class and set the control to its pristine
-   * state (ng-pristine class). A model is considered to be pristine when the model has not been changed
-   * from when first compiled within then form.
+   * This method can be called to remove the `ng-dirty` class and set the control to its pristine
+   * state (`ng-pristine` class). A model is considered to be pristine when the control
+   * has not been changed from when first compiled.
    */
   this.$setPristine = function() {
     ctrl.$dirty = false;
@@ -1898,8 +1901,8 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
    * @description
    * Sets the control to its untouched state.
    *
-   * This method can be called to remove the 'ng-touched' class and set the control to its
-   * untouched state (ng-untouched class). Upon compilation, a model is set as untouched
+   * This method can be called to remove the `ng-touched` class and set the control to its
+   * untouched state (`ng-untouched` class). Upon compilation, a model is set as untouched
    * by default, however this function can be used to restore that state if the model has
    * already been touched by the user.
    */
@@ -1916,10 +1919,9 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
    * @description
    * Sets the control to its touched state.
    *
-   * This method can be called to remove the 'ng-untouched' class and set the control to its
-   * touched state (ng-touched class). A model is considered to be touched when the user has
-   * first interacted (focussed) on the model input element and then shifted focus away (blurred)
-   * from the input element.
+   * This method can be called to remove the `ng-untouched` class and set the control to its
+   * touched state (`ng-touched` class). A model is considered to be touched when the user has
+   * first focused the control element and then shifted focus away from the control (blur event).
    */
   this.$setTouched = function() {
     ctrl.$touched = true;