Update references for latest bugfix releases

- Point 'Latest Release' on homepage at 3.1.5
- Add Elasticsearch updates (7.7.x) support to ES info page
- Update '/releases-readme' page to indicate latest release as 3.1.5

Change-Id: I874318008ab6441282182d1f1754d243b48115e6
diff --git a/index.md b/index.md
index f77c5f7..6ca70db 100644
--- a/index.md
+++ b/index.md
@@ -68,9 +68,9 @@
                 <div class="panel-body">
                     <h4>Download</h4>
                     <p>Our latest release is:<br>
-                    <b><a href="3.1.html">3.1.4</a></b>
+                    <b><a href="3.1.html">3.1.5</a></b>
                     </p>
-                    <a href="https://gerrit-releases.storage.googleapis.com/gerrit-3.1.4.war" class="btn btn-primary">Download</a>
+                    <a href="https://gerrit-releases.storage.googleapis.com/gerrit-3.1.5.war" class="btn btn-primary">Download</a>
                 </div>
             </div>
         </div>
diff --git a/pages/site/elasticsearch.md b/pages/site/elasticsearch.md
index a378d3f..7ca70e5 100644
--- a/pages/site/elasticsearch.md
+++ b/pages/site/elasticsearch.md
@@ -26,6 +26,7 @@
 | 7.4.x                 | 2.16.13 | 3.0.3 | 3.1.0 | 3.2.0 |                                                  |
 | 7.5.x                 | 2.16.14 | 3.0.5 | 3.1.1 | 3.2.0 |                                                  |
 | 7.6.x                 | 2.16.17 | 3.0.8 | 3.1.4 | 3.2.0 |                                                  |
+| 7.7.x                 | 2.16.19 | 3.0.9 | 3.1.5 | 3.2.0 |                                                  |
 
 Indices created in Elasticsearch 5.x or earlier will need to be reindexed with
 Elasticsearch 6.x in order to be readable by Elasticsearch 7.x. See
diff --git a/pages/site/releases/README.md b/pages/site/releases/README.md
index a9bed9d..0f04bb1 100644
--- a/pages/site/releases/README.md
+++ b/pages/site/releases/README.md
@@ -15,7 +15,7 @@
 Artifacts deployed to Maven Central are signed with the maintainer's key.
 Please refer to the [list of maintainers' keys](/public-keys.html).
 
-Latest release: **[3.1.4](/3.1.html)**. The support status of all recent Gerrit versions is
+Latest release: **[3.1.5](/3.1.html)**. The support status of all recent Gerrit versions is
 [summarized here](https://www.gerritcodereview.com/support.html#supported-versions).
 
 ## 3.3.0 (in development)