docs(ngForm): fix grammar and improve explanation

Closes #4050

Author: jdavisp3

src/ng/directive/form.js

@@ -217,15 +217,19 @@ function FormController(element, attrs) {
  * Directive that instantiates
  * {@link ng.directive:form.FormController FormController}.
  *
- * If `name` attribute is specified, the form controller is published onto the current scope under
+ * If the `name` attribute is specified, the form controller is published onto the current scope under
  * this name.
  *
  * # Alias: {@link ng.directive:ngForm `ngForm`}
  *
- * In angular forms can be nested. This means that the outer form is valid when all of the child
- * forms are valid as well. However browsers do not allow nesting of `<form>` elements, for this
- * reason angular provides {@link ng.directive:ngForm `ngForm`} alias
- * which behaves identical to `<form>` but allows form nesting.
+ * In Angular forms can be nested. This means that the outer form is valid when all of the child
+ * forms are valid as well. However, browsers do not allow nesting of `<form>` elements, so
+ * Angular provides the {@link ng.directive:ngForm `ngForm`} directive which behaves identically to
+ * `<form>` but can be nested.  This allows you to have nested forms, which is very useful when
+ * using Angular validation directives in forms that are dynamically generated using the
+ * {@link ng.directive:ngRepeat `ngRepeat`} directive. Since you cannot dynamically generate the `name`
+ * attribute of input elements using interpolation, you have to wrap each set of repeated inputs in an
+ * `ngForm` directive and nest these in an outer `form` element.
  *
  *
  * # CSS classes
@@ -235,12 +239,12 @@ function FormController(element, attrs) {
  *  - `ng-dirty` Is set if the form is dirty.
  *
  *
- * # Submitting a form and preventing default action
+ * # Submitting a form and preventing the default action
  *
  * Since the role of forms in client-side Angular applications is different than in classical
  * roundtrip apps, it is desirable for the browser not to translate the form submission into a full
  * page reload that sends the data to the server. Instead some javascript logic should be triggered
- * to handle the form submission in application specific way.
+ * to handle the form submission in an application-specific way.
  *
  * For this reason, Angular prevents the default action (form submission to the server) unless the
  * `<form>` element has an `action` attribute specified.
@@ -252,8 +256,9 @@ function FormController(element, attrs) {
  * - {@link ng.directive:ngClick ngClick} directive on the first
   *  button or input field of type submit (input[type=submit])
  *
- * To prevent double execution of the handler, use only one of ngSubmit or ngClick directives. This
- * is because of the following form submission rules coming from the html spec:
+ * To prevent double execution of the handler, use only one of the {@link ng.directive:ngSubmit ngSubmit}
+ * or {@link ng.directive:ngClick ngClick} directives.
+ * This is because of the following form submission rules in the HTML specification:
  *
  * - If a form has only one input field then hitting enter in this field triggers form submit
  * (`ngSubmit`)