Fix uses of loading spinner (#2797)

* Update Loading Indicator

- Fix mistake in LoadingIndicator Less
- Middle align the loading indicator when inline
- Fix Loading Indicator not correctly accepting container class names
- Add inline and block attributes

* Fix loading indicator in composer

* Fix loading indicator on notification list

* Fix loading indicator on discussion page

* Fix loading indicator on button

* Update more uses of loading indicator

* Fix loading indicator in Search box

* Fix AvatarEditor loading spinner

* Set default spinner props

* Replace "tiny" with "small" in Less

* Improve spinner vertical centring in buttons

* Reduce size specificity

* Use single attribute for block/inline

* Use new display attribute

* Use classes for different sizes

* Use `display=block` by default

js/src/forum/components/DiscussionList.js

@@ -19,7 +19,7 @@ export default class DiscussionList extends Component {
     let loading;
 
     if (state.isLoading()) {
-      loading = LoadingIndicator.component();
+      loading = <LoadingIndicator />;
     } else if (state.moreResults) {
       loading = Button.component(
         {