Update AdminLTE

- from 2.4.5 to 2.4.18 (cannot detect any issues)
- set default scancycle for Apple Devices to 1

front/lib/AdminLTE/build/less/variables.less

@@ -102,6 +102,11 @@
 // Border radius for non flat buttons
 @btn-border-radius: 3px;
 
+// HR
+// --------------------------------------------------------
+// Horizontal line color.
+@hr-border: @gray;
+
 // DIRECT CHAT
 // --------------------------------------------------------
 @direct-chat-height: 250px;