feature #3719 Fixed event listeners priority (tony-co)

This PR was submitted for the master branch but it was merged into the 2.3 branch instead (closes #3719).

Discussion
----------

Fixed event listeners priority

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

Commits
-------

47d4d4f Fixed title level consistency
1dbfd29 Updated title for the core cache warmers
a9d07a5 Fixed title underline
815f531 Replaced the priority paragraph with a note and a table
db2c002 Fixed event listeners priority (typos after review)
13b5645 Fixed event listeners priority

reference/dic_tags.rst

@@ -463,9 +463,23 @@ To register your warmer with Symfony, give it the ``kernel.cache_warmer`` tag:
             ->addTag('kernel.cache_warmer', array('priority' => 0))
         ;
 
-The ``priority`` value is optional, and defaults to 0. This value can be
-from -255 to 255, and the warmers will be executed in the order of their
-priority.
+.. note::
+
+    The ``priority`` value is optional, and defaults to 0.
+    The higher the priority, the sooner it gets executed.
+
+Core Cache Warmers
+~~~~~~~~~~~~~~~~~~
+
++-------------------------------------------------------------------------------------------+-----------+
+| Cache Warmer Class Name                                                                   | Priority  |
++-------------------------------------------------------------------------------------------+-----------+
+| :class:`Symfony\\Bundle\\FrameworkBundle\\CacheWarmer\\TemplatePathsCacheWarmer`          | 20        |
++-------------------------------------------------------------------------------------------+-----------+
+| :class:`Symfony\\Bundle\\FrameworkBundle\\CacheWarmer\\RouterCacheWarmer`                 | 0         |
++-------------------------------------------------------------------------------------------+-----------+
+| :class:`Symfony\\Bundle\\TwigBundle\\CacheWarmer\\TemplateCacheCacheWarmer`               | 0         |
++-------------------------------------------------------------------------------------------+-----------+
 
 .. _dic-tags-kernel-event-listener: