Don’t force wrapping when focusing in a direction would work (+test)

Think of the following layout:

 -------------
 | tab |     |
 | con | win |
 |     |     |
 -------------

The tabbed container on the left has two children. Assume you have focused the
second/right child in the tabbed container. i3 used to focus the first/left
container of the tabbed container when using 'focus right' (it wrapped focus).

With this commit, the default behaviour is to instead focus the window on the
right of the screen.

The intention is to make focus switching more intuitive, especially with tabbed
containers supporting 'focus left'/'focus right' in tree. You should end up
using less 'focus parent' :).

You can force the old behaviour with 'force_focus_wrapping true' in your
config.

Code coverage is 62.5% with this commit.

include/config.h

@@ -111,6 +111,16 @@ struct Config {
          * comes with i3. Thus, you can turn it off entirely. */
         bool disable_workspace_bar;
 
+        /** Think of the following layout: Horizontal workspace with a tabbed
+         * con on the left of the screen and a terminal on the right of the
+         * screen. You are in the second container in the tabbed container and
+         * focus to the right. By default, i3 will set focus to the terminal on
+         * the right. If you are in the first container in the tabbed container
+         * however, focusing to the left will wrap. This option forces i3 to
+         * always wrap, which will result in you having to use "focus parent"
+         * more often. */
+        bool force_focus_wrapping;
+
         /** The default border style for new windows. */
         border_style_t default_border;