Add summary view to the /activity report.

When you load the activity report, it will just show summary
counts for realms, but if you click on a realm, you will see
details about users in the realms.  You can also click "Show all"
to see an interleaved view of realms and users.

(imported from commit b106557b1fae64d525071afc124b5a8aed319086)

static/js/activity_page.js

@@ -0,0 +1,45 @@
+$(function () {
+    function show_realms_only() {
+        $(".table").each(function () {
+            var table = $(this);
+
+            table.find('tbody tr[data-type="user"]').hide();
+            table.find('tbody tr[data-type="realm"]').show();
+        });
+    }
+
+    function filter_to_realm(realm) {
+        $(".table").each(function () {
+            var table = $(this);
+
+            table.find("tbody tr").hide();
+            var rows = table.find('tbody tr[data-realm="'+realm+'"]');
+            rows.show();
+        });
+
+    }
+
+    function set_up_realm_links() {
+        $("a.realm").on("click", function () {
+            var realm = $(this).attr("data-realm");
+            filter_to_realm(realm);
+        });
+    }
+
+    function set_up_summary_link() {
+        $("a.show-summary").on("click", function () {
+            show_realms_only();
+        });
+    }
+
+    function set_up_show_all_link() {
+        $("a.show-all").on("click", function () {
+            $(".table tbody tr").show();
+        });
+    }
+
+    show_realms_only();
+    set_up_realm_links();
+    set_up_summary_link();
+    set_up_show_all_link();
+});