GEODE-2110 Add gfsh start server user and password options

Modifies gfsh start server command reference page to add
the two missing options: --user and --password

geode-docs/tools_modules/gfsh/command-pages/start.html.md.erb

@@ -501,6 +501,7 @@ start server --name=value [--assign-buckets(=value)] [--bind-address=value]
     [--socket-buffer-size=value] [--lock-memory=value] [--off-heap-memory-size=value]
     [--start-rest-api=value]
     [--http-service-port=value] [--http-service-bind-address=value]
+    [--user=value] [--password=value]
 ```
 
 <a id="topic_3764EE2DB18B4AE4A625E0354471738A__table_at5_bwg_2w"></a>
@@ -763,6 +764,20 @@ See <a href="../../../configuring/cluster_config/gfsh_persist.html">Overview of
 </td>
 <td>all local addresses</td>
 </tr>
+<tr class="even">
+<td><span class="keyword parmname">\-\-user</span></td>
+<td>The user name of the credential to use in authenticating to the cluster.
+When specified, if the <code>--password</code> option is not also specified,
+then <code>gfsh</code> will prompt for the password.
+</td>
+<td></td>
+</tr>
+<tr class="even">
+<td><span class="keyword parmname">\-\-password</span></td>
+<td>The password portion of the credential to use in authenticating to the cluster.
+</td>
+<td></td>
+</tr>
 </tbody>
 </table>