docs(dialog): added docs to the elements and fixed controller

Added `md-dialog` directive page that contains - `md-dialog`, `md-dialog-content`, `md-dialog-actions`.
Added `function` type to controller method

fixes #4728 and #3199

Closes #5957

src/components/dialog/dialog.js

@@ -10,6 +10,39 @@ angular
   .directive('mdDialog', MdDialogDirective)
   .provider('$mdDialog', MdDialogProvider);
 
+/**
+ * @ngdoc directive
+ * @name mdDialog
+ * @module material.components.dialog
+ *
+ * @restrict E
+ *
+ * @description
+ * `<md-dialog>` - The dialog's template must be inside this element.
+ *
+ * Inside, use an `<md-dialog-content>` element for the dialog's content, and use
+ * an `<md-dialog-actions>` element for the dialog's actions.
+ *
+ * * ## CSS
+ * - `.md-dialog-content` - class that sets the padding on the content as the spec file
+ *
+ * @usage
+ * ### Dialog template
+ * <hljs lang="html">
+ * <md-dialog aria-label="List dialog">
+ *   <md-dialog-content>
+ *     <md-list>
+ *       <md-list-item ng-repeat="item in items">
+ *         <p>Number {{item}}</p>
+ *       </md-list-item>
+ *     </md-list>
+ *   </md-dialog-content>
+ *   <md-dialog-actions>
+ *     <md-button ng-click="closeDialog()" class="md-primary">Close Dialog</md-button>
+ *   </md-dialog-actions>
+ * </md-dialog>
+ * </hljs>
+ */
 function MdDialogDirective($$rAF, $mdTheming, $mdDialog) {
   return {
     restrict: 'E',
@@ -66,7 +99,7 @@ function MdDialogDirective($$rAF, $mdTheming, $mdDialog) {
  * - Complex dialogs can be sized with `flex="percentage"`, i.e. `flex="66"`.
  * - Default max-width is 80% of the `rootElement` or `parent`.
  *
- * ## Css
+ * ## CSS
  * - `.md-dialog-content` - class that sets the padding on the content as the spec file
  *
  * @usage
@@ -372,7 +405,7 @@ function MdDialogDirective($$rAF, $mdTheming, $mdDialog) {
  *   - `focusOnOpen` - `{boolean=}`: An option to override focus behavior on open. Only disable if
  *     focusing some other way, as focus management is required for dialogs to be accessible.
  *     Defaults to true.
- *   - `controller` - `{string=}`: The controller to associate with the dialog. The controller
+ *   - `controller` - `{function|string=}`: The controller to associate with the dialog. The controller
  *     will be injected with the local `$mdDialog`, which passes along a scope for the dialog.
  *   - `locals` - `{object=}`: An object containing key/value pairs. The keys will be used as names
  *     of values to inject into the controller. For example, `locals: {three: 3}` would inject