RMQ-1263: Shovel Management - add help strings for shovel counters

(cherry picked from commit 8e79a7f500c2df355f3ec7ac1fa1bdd3a8dff6a4)
(cherry picked from commit 9efa0d9)

Author: ikavgo

deps/rabbitmq_shovel_management/priv/www/js/shovel.js

@@ -148,6 +148,19 @@ HELP['shovel-amqp10-auto-delete'] =
        <dt><code>After num messages</code></dt>\
        <dd>The shovel will delete itself after the given number of messages have been transferred.</dd>\
 </dl>';
+
+HELP['shovel-remaining-counter'] =
+    'When not <code>unlimited</code>: number of messages left to transfer before this shovel will be deleted.';
+
+HELP['shovel-remaining-unacked-counter'] =
+    'When ack mode is <code>on-confirm</code> and Remaining is not <code>unlimited</code>: number of messages not yet acknowledged at the source.';
+
+HELP['shovel-pending-counter'] =
+    'When destination connection is blocked or doesn\'t have enough credits: number of messages that were cached.';
+
+HELP['shovel-forwarded-counter'] =
+    'Number of forwarded messages.';
+
 function remove_params_with(sammy, prefix) {
     for (var i in sammy.params) {
         if(i.startsWith(prefix)) {

deps/rabbitmq_shovel_management/priv/www/js/tmpl/shovels.ejs

@@ -17,10 +17,10 @@
     <th>Virtual Host</th>
 <% } %>
     <th>State</th>
-    <th>Remaining</th>
-    <th>Remaining Unacked</th>
-    <th>Pending</th>
-    <th>Forwarded</th>
+    <th>Remaining <span class="help" id="shovel-remaining-counter"></span></th>
+    <th>Remaining Unacked <span class="help" id="shovel-remaining-unacked-counter"></span></th>
+    <th>Pending <span class="help" id="shovel-pending-counter"></span></th>
+    <th>Forwarded <span class="help" id="shovel-forwarded-counter"></span></th>
     <th colspan="3">Source</th>
     <th colspan="3">Destination</th>
     <th>Last changed</th>