[book] [routing] used the American term "bidirectional"
instead of the British bi-directional
[book] [routing] reworded the note about generating URLs in console
[book] [routing] fixed a note that wasn't properly updated

Previously, the code used the generate() method of the service and
the note explained the generateUrl() method of the base controller.
Then, the example was updated to use the generateUrl(), but the
note kept explaining the generateUrl(). This change is just about
explaining in the note the alterantive generate() method of the service.
[book] [routing] minor rewording and fixed some sample code
minor #3736 [book] Misc. routing fixes (javiereguiluz)

This PR was merged into the 2.3 branch.

Discussion
----------

[book] Misc. routing fixes

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.3+
| Fixed tickets | -

Commits
-------

7500435 [book] [routing] minor rewording and fixed some sample code
26f9e3b [book] [routing] fixed a note that wasn't properly updated
355cd5b [book] [routing] reworded the note about generating URLs in console
da8b46f [book] [routing] used the American term "bidirectional" instead of the British bi-directional