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

less/common/Search.less

@@ -8,7 +8,8 @@
     &.focused {
       margin-left: -400px;
 
-      input, .Search-results {
+      input,
+      .Search-results {
         width: 400px;
       }
     }
@@ -61,11 +62,21 @@
     .transition(all 0.4s);
     box-sizing: inherit !important;
   }
+
+  .LoadingIndicator-container {
+    height: 36px;
+  }
+
   .Button {
     float: left;
     margin-left: -36px;
-    width: 36px !important;
     outline: none;
+    width: 36px !important;
+
+    &.LoadingIndicator {
+      width: var(--size) !important;
+      padding: 0;
+    }
   }
 }