Put the release notes description label inside a Gtk.Grid

This is the same issue that we had for issues, but now for the description label itself. It seems that in a Gtk.Box with wrapped labels will not do its height correctly, if there are grids abound.

Putting the label inside a Gtk.Grid will make it also respect the natural height and will fix another set of problems found in other description labels.

src/Widgets/ReleaseRow.vala

@@ -29,8 +29,17 @@ public class AppCenter.Widgets.ReleaseRow : Gtk.Box {
     }
 
     construct {
-        var header_icon = new Gtk.Image.from_icon_name ("tag-symbolic");
+        orientation = Gtk.Orientation.VERTICAL;
+        spacing = 6;
+        margin_bottom = 6;
+
+        create_header ();
+        create_description ();
+        create_issues ();
+    }
 
+    private void create_header () {
+        var header_icon = new Gtk.Image.from_icon_name ("tag-symbolic");
         var header_label = new Gtk.Label (format_version (release.get_version ())) {
             use_markup = true
         };
@@ -42,32 +51,40 @@ public class AppCenter.Widgets.ReleaseRow : Gtk.Box {
         };
         date_label.add_css_class (Granite.STYLE_CLASS_DIM_LABEL);
 
+        var header_grid = new Gtk.Grid () {
+            column_spacing = 6,
+            row_spacing = 6,
+            margin_bottom = 6
+        };
+        header_grid.attach (header_icon, 0, 0);
+        header_grid.attach (header_label, 1, 0);
+        header_grid.attach (date_label, 2, 0);
+
+        append (header_grid);
+    }
+
+    private void create_description () {
         var description_label = new Gtk.Label (format_release_description (release.get_description ())) {
             selectable = true,
             use_markup = true,
             max_width_chars = 55,
             wrap = true,
-            xalign = 0
+            xalign = 0,
         };
         description_label.add_css_class (Granite.STYLE_CLASS_H3_LABEL);
 
-        var grid = new Gtk.Grid () {
+        var description_grid = new Gtk.Grid () {
             column_spacing = 6,
             row_spacing = 6,
             margin_bottom = 6
         };
-        grid.attach (header_icon, 0, 0);
-        grid.attach (header_label, 1, 0);
-        grid.attach (date_label, 2, 0);
-        grid.attach (description_label, 0, 1, 3);
+        description_grid.attach (description_label, 0, 0);
 
-        orientation = Gtk.Orientation.VERTICAL;
-        spacing = 6;
-
-        append (grid);
+        append (description_grid);
+    }
 
+    private void create_issues () {
         var issues = release.get_issues ();
-
         if (issues.length > 0) {
             var issue_header = new Gtk.Label (_("Fixed Issues")) {
                 halign = Gtk.Align.START,