[11.0][FIX][web_group_expand] Fix issue #987 & Improvements (#993)

* Fixes issue #987
* Follow new readme structure
* Use Less
* Hide expand/collapse buttons if select a view type that isn't a 'list'

web_group_expand/static/src/less/web_group_expand.less

@@ -0,0 +1,10 @@
+.o_favorites_menu {
+    +.toggle_buttons {
+        float: left;
+        padding-left: 5px;
+
+        button {
+            display: inline;
+        }
+    }
+}