[gnome-calendar/gnome-3-26] Bump 3.26.0 release

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 5749d6e4301ddab4014076d5a262e06945fde5cf
Author: Georges Basile Stavracas Neto <georges stavracas gmail com>
Date:   Mon Sep 11 23:13:47 2017 -0300

    Bump 3.26.0 release

 NEWS                                           |   10 ++++++++++
 data/appdata/org.gnome.Calendar.appdata.xml.in |   21 +++++++++++++++++++++
 2 files changed, 31 insertions(+), 0 deletions(-)
---
diff --git a/NEWS b/NEWS
index 8802b02..1a47e7d 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,13 @@
+Major changes in 3.26.0:
+* Many fixes to recurrent events (Yash Singh, Georges Basile Stavracas Neto)
+* Cache events for better resource management
+* Improve organization of files in the source code
+* Handle command line options correctly (Mohammed Sadiq)
+* Added the first version of a test suite. This will allow us continue improving
+  and delivering new features with much less regressions.
+* Many code cleanups and reorganizations.
+* Updated translations for many languages.
+
 Major changes in 3.25.90:
 * Port to Meson build system (Iñigo Martínez)
 * Improve string in the quick add popover (Carlo Lobrano)
diff --git a/data/appdata/org.gnome.Calendar.appdata.xml.in b/data/appdata/org.gnome.Calendar.appdata.xml.in
index 2298217..2c26340 100644
--- a/data/appdata/org.gnome.Calendar.appdata.xml.in
+++ b/data/appdata/org.gnome.Calendar.appdata.xml.in
@@ -49,6 +49,27 @@
   <project_group>GNOME</project_group>
 
   <releases>
+    <release date="2017-09-11" version="3.26.0">
+      <description>
+        <p>
+          The GNOME Calendar team is proud to announce the 3.26.0 release of GNOME Calendar,
+          the first stable release of the 3.26 cycle! This release brings hundreds of improvements
+          from more than 50 different contributors.
+        </p>
+        <p>
+          The biggest highlight of this release is the introduction of support for events with
+          recurrences. This was the result of a successfull Google Summer of Code project, and
+          makes managing events that repeat over time much smoother.
+        </p>
+        <p>
+          This release also brings dozens of corrections from new contributors, and improves the
+          memory consumption of Calendar.
+        </p>
+        <p>This release also updates many translations.</p>
+        <p>Thanks to all the contributors that worked on GNOME Calendar!</p>
+      </description>
+    </release>
+
     <release date="2017-08-11" version="3.25.90">
       <description>
         <p>