GUACAMOLE-724: Render menu and client tile headers above client-specific modals.

guacamole/src/main/frontend/src/app/client/styles/menu.css

@@ -26,7 +26,7 @@
     width: 480px;
     background: #EEE;
     box-shadow: inset -1px 0 2px white, 1px 0 2px black;
-    z-index: 10;
+    z-index: 100;
     -webkit-transition: left 0.125s, opacity 0.125s;
     -moz-transition: left 0.125s, opacity 0.125s;
     -ms-transition: left 0.125s, opacity 0.125s;

guacamole/src/main/frontend/src/app/client/styles/tiled-client-grid.css

@@ -80,6 +80,7 @@
     padding: 0 0.25em;
     font-size: 0.8em;
     color: white;
+    z-index: 30;
 }
 
 .tiled-client-grid .client-tile.focused .client-tile-name {