Add an endpoint for downloading the logs of a build.

static/directives/build-logs-view.html

@@ -3,6 +3,12 @@
     <i class="fa fa-clipboard"></i>Copy Logs
   </button>
 
+  <a id="downloadButton" class="btn btn-primary download-button"
+     ng-href="/buildlogs/{{ currentBuild.id }}"
+     target="_blank">
+    <i class="fa fa-download"></i>Download Logs
+  </a>
+
   <span class="cor-loader" ng-if="!logEntries"></span>
 
   <span class="no-logs" ng-if="!logEntries.length && currentBuild.phase == 'waiting'">