Add branch to Zuul dashboard

It's very inconvenient to check the branch in a build by
looking at the job url.

We already receive the object branch according to the JSON answer
I receive from my browser, so it's just a question of displaying
it.

Change-Id: I21cfbf1c765f6c03cc8db9e82fc829142adb6de6

web/templates/builds.ejs

@@ -48,6 +48,7 @@ under the License.
       <tr>
         <th>Job</th>
         <th>Project</th>
+        <th>Branch</th>
         <th>Pipeline</th>
         <th>Change</th>
         <th>Duration</th>
@@ -60,6 +61,7 @@ under the License.
       <tr ng-repeat="build in builds" ng-class="rowClass(build)">
         <td>{{ build.job_name }}</td>
         <td>{{ build.project }}</td>
+        <td>{{ build.branch }}</td>
         <td>{{ build.pipeline }}</td>
         <td><a href="{{ build.ref_url }}" target="_self">change</a></td>
         <td>{{ build.duration }} seconds</td>