minor #8313 Improve routing debug page (Ahmed TAILOULOUTE, javiereguiluz)

This PR was submitted for the 2.7 branch but it was merged into the 2.8 branch instead (closes #8313).

Discussion
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Improve routing debug page

Some small improvement for the routing debug doc (http://symfony.com/doc/2.7/routing/debug.html)

Commits
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6d62d60 Fixes and simplifications
7b2d5d0 Improve routing debug page

Author: javiereguiluz

routing/debug.rst

@@ -18,12 +18,16 @@ your application:
 
 .. code-block:: text
 
-    homepage              ANY       /
-    contact               GET       /contact
-    contact_process       POST      /contact
-    article_show          ANY       /articles/{_locale}/{year}/{title}.{_format}
-    blog                  ANY       /blog/{page}
-    blog_show             ANY       /blog/{slug}
+    ------------------ -------- -------- ------ ----------------------------------------------
+     Name               Method   Scheme   Host   Path
+    ------------------ -------- -------- ------ ----------------------------------------------
+     homepage           ANY      ANY      ANY    /
+     contact            GET      ANY      ANY    /contact
+     contact_process    POST     ANY      ANY    /contact
+     article_show       ANY      ANY      ANY    /articles/{_locale}/{year}/{title}.{_format}
+     blog               ANY      ANY      ANY    /blog/{page}
+     blog_show          ANY      ANY      ANY    /blog/{slug}
+    ------------------ -------- -------- ------ ----------------------------------------------
 
 You can also get very specific information on a single route by including
 the route name after the command: