add tooltip to show why host groups radio is disabled

share/public/css/netdisco.css

@@ -445,6 +445,15 @@ td > form.nd_inline-form {
   margin-left: 7px;
 }
 
+/* to allow display of tooltip on a disabled control
+   http://jsfiddle.net/cSSUA/209/ */
+.tooltip-wrapper {
+  display: inline-block;
+}
+.tooltip-wrapper .input[disabled] {
+  pointer-events: none;
+}
+
 /* vlan entry box for netmap */
 #nd_vlan-label {
   margin-left: 5px;

share/views/sidebar/device/netmap.tt

@@ -60,7 +60,12 @@
                 <label for="nd_mapshow-neighbors">Neighbors Only</label>
             </div>
 
+            [% IF devgrp_list.size %]
             <div class="radio radio-success">
+            [% ELSE %]
+            <div class="radio radio-success tooltip-wrapper"
+                rel="tooltip" data-placement="left" data-offset="5" data-title="No Named Groups Defined">
+            [% END %]
                 <input type="radio" name="mapshow" id="nd_mapshow-only"
                 [% 'checked' IF vars.sidebar_defaults.device_netmap.mapshow == 'only' %]
                 [% 'disabled' IF NOT devgrp_list.size %] value="only">