Tutorial improvements

- Skip the build-related tutorial steps when builds are disabled
- Make the styling of the tutorial more consistent with the new layout

static/tutorial/welcome.html

@@ -1,10 +1,11 @@
 <p>This tutorial will walk you step-by-step through using <span class="registry-name"></span>, covering:
 <ul>
-<li>Logging into <span class="registry-name"></span> from Docker</li>
+<li>Logging into <span class="registry-name"></span> from the Docker CLI</li>
 <li>Starting a container</li>
 <li>Creating images from a container</li>
 <li>Pushing a repository to <span class="registry-name"></span></li>
 <li>Viewing a repository</li>
+<li quay-require="['BUILD_SUPPORT']">Setting up build triggers</li>
 <li>Changing a repository's permissions</li>
 </ul>
 </p>