split up PowerLevelEditor into two components

one while editing (PowerLevelEditor) and one
while not editing (PowerLevelSection).

Also save when pressing the button, not when changing the
power dropdown.

Also show the spinner next to the dropdown when saving,
not at the bottom of the component.

res/css/views/right_panel/_UserInfo.scss

@@ -132,8 +132,8 @@ limitations under the License.
 
         margin: 6px 0;
 
-        .mx_IconButton {
-            margin-left: 6px;
+        .mx_IconButton, .mx_Spinner {
+            margin-left: 20px;
             width: 16px;
             height: 16px;
 
@@ -148,6 +148,10 @@ limitations under the License.
             align-items: center;
             // try to make it the same height as the dropdown
             margin: 11px 0 12px 0;
+
+            .mx_IconButton {
+                margin-left: 6px;
+            }
         }
 
         .mx_Field {