source-dialog: use a builder .ui definition for interface

We know that coding interfaces sucks, so use a .ui file instead.

data/Makefile.am

@@ -49,6 +49,7 @@ EXTRA_DIST=                     \
   org.gnome.Calendar.desktop    \
   calendar.gresource.xml        \
   shell-search-provider-dbus-interfaces.xml \
+  ui/calendar-row.ui            \
   ui/date-selector.ui           \
   ui/edit-dialog.ui             \
   ui/menus.ui                   \

data/calendar.gresource.xml

@@ -1,6 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <gresources>
   <gresource prefix="/org/gnome/calendar">
+    <file alias="calendar-row.ui" compressed="true" preprocess="xml-stripblanks">ui/calendar-row.ui</file>
     <file alias="date-selector.ui" compressed="true" preprocess="xml-stripblanks">ui/date-selector.ui</file>
     <file alias="edit-dialog.ui" compressed="true" preprocess="xml-stripblanks">ui/edit-dialog.ui</file>
     <file alias="menus.ui" compressed="true" preprocess="xml-stripblanks">ui/menus.ui</file>

data/ui/calendar-row.ui

@@ -0,0 +1,56 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!-- Generated with glade 3.18.1 -->
+<interface>
+  <requires lib="gtk+" version="3.16"/>
+  <object class="GtkListBoxRow" id="row">
+    <property name="width_request">100</property>
+    <property name="visible">True</property>
+    <property name="can_focus">True</property>
+    <child>
+      <object class="GtkGrid" id="grid">
+        <property name="visible">True</property>
+        <property name="can_focus">False</property>
+        <property name="border_width">6</property>
+        <property name="column_spacing">12</property>
+        <child>
+          <object class="GtkImage" id="icon">
+            <property name="visible">True</property>
+            <property name="can_focus">False</property>
+            <property name="pixel_size">24</property>
+          </object>
+          <packing>
+            <property name="left_attach">0</property>
+            <property name="top_attach">0</property>
+            <property name="height">2</property>
+          </packing>
+        </child>
+        <child>
+          <object class="GtkLabel" id="subtitle">
+            <property name="visible">True</property>
+            <property name="can_focus">False</property>
+            <property name="hexpand">True</property>
+            <property name="xalign">0</property>
+            <style>
+              <class name="dim-label"/>
+            </style>
+          </object>
+          <packing>
+            <property name="left_attach">1</property>
+            <property name="top_attach">1</property>
+          </packing>
+        </child>
+        <child>
+          <object class="GtkLabel" id="title">
+            <property name="visible">True</property>
+            <property name="can_focus">False</property>
+            <property name="xalign">0</property>
+          </object>
+          <packing>
+            <property name="left_attach">1</property>
+            <property name="top_attach">0</property>
+          </packing>
+        </child>
+      </object>
+    </child>
+  </object>
+</interface>