fix(icon) add loading css

www/Themes/Centreon-2/centreon-loading.css

+/******* Loading containers **********/
+
+.loadingWrapper {
+  position: absolute;
+  top: 0;
+  left: 0;
+  background: rgba(255,255,255,0.5);
+  width: 100%;
+  height: 100%;
+  transition: all ease 0.6s;
+}
+
 .waiting {
   position: relative;
   height: 100%;