Add link and info for app-catalog-ui horizon plugin

This commit adds a link to and some language about the
App Catalog Horizon plugin.

Author:         Christopher Aedo <doc@aedo.net>
Co-Authored-By: Kevin Fox <kevin@efox.cc>

Change-Id: Ifbf9b419af36c1bac23e59e0bfe4efc57a0c9b1a

LICENSE

@@ -1,3 +1,7 @@
+Some files from:
+http://www.iconarchive.com/show/beautiful-flat-icons-by-elegantthemes/plugin-icon.html
+
+Everything else:
 
                                  Apache License
                            Version 2.0, January 2004

openstack_catalog/web/index.html

@@ -131,6 +131,17 @@
               <p>OpenShift</p></a>
             </div>
           </div>
+    </div>
+    <div class="row pluginbox">
+      <div class="col-sm-2">
+          <a href="https://github.com/openstack/app-catalog-ui" target="_blank">
+          <img src="static/images/plugin-icon.png">
+          <div class='lbl'>Horizon Plugin</div>
+          </a>
+      </div><div class="col-sm-10">
+        <p><strong>Want this catalog included in your OpenStack environment?</strong></p>
+        <p>There is a Horizon plugin available at <a href="https://github.com/openstack/app-catalog-ui" target="_blank">https://github.com/openstack/app-catalog-ui</a> which gives users the ability to search and retrieve App Catalog contents directly from Horizon &mdash; add it to your environment today!</p>
+      </div>
     </div>
         <p><strong>Don't have OpenStack yet?</strong></p>
         <p>Visit the <a href="https://www.openstack.org/marketplace/" target="_blank">OpenStack Marketplace</a> and select tools and methods for building your cloud. Then come back to the OpenStack Application Catalog to make your cloud sing with applications.</p>

openstack_catalog/web/static/css/theme.css

@@ -127,6 +127,14 @@ a.details i {
     margin-bottom: 0;
     font-size: .9em;
 }
+.pluginbox {
+    background-color: #edf2f7;
+    padding: 20px;
+    margin: 20px 0;
+}
+.pluginbox .lbl {
+    text-align: center;
+}
 .title div {
     font-size: 18px;
     text-transform: uppercase;