[ticket/11366] Extension's version's check

Add a feature to check automatically the version of the installed
extensions. The informations are cached for 24 hours (like for the
global update check on the main page of the acp).

The informations about the versions are display both on the global list
and on the detailled page.

To do this the developper has to to let the composer.json of the latest
version available and add some informations into it :

    "extra": {
		"version-check": {
			"host": "<the host>",
			"directory": "<the directory containing the file>",
			"filename": "<the composer.json of the latest version>"
		}
    }

He can also add two extra informations which will be displayed if a new
version is available :

	"extra": {
		"download": "<download link>",
		"annoucement": "<announcement link>",
    }

Currently a notice is displayed when the "extra.version-check"
informations are
missing.

Ticket: https://tracker.phpbb.com/browse/PHPBB3-11366

Signed-off-by: Nicofuma <github@nicofuma.fr>

PHPBB3-11366
[ticket/11366] Moving to \phpbb\version_helper

+ bug fix (missing exception)
+ Using \phpbb\version_helper
So, now, the version file have a new format :

	{
		"stable": {
			"<branch>": {
				"current": "<version>",
				[ "announcement": "<announcement link>", ]
				[ "download": "<download link>", ]
			},
			"<branch>": {
				...
			}
		},
		"unstable": {
		}
	}

PHPBB3-11366
[ticket/11366] Bug Fix: Extensions removed but still registred in DB

Fix the bug with the Extensions removed but still registred in DB

PHPBB3-11366
[ticket/11366] Adding a missing commit

PHPBB3-11366
[ticket/11366] Set the size of the 'current version' column to 20%

PHPBB3-11366
[ticket/11366] Remove unused langage entry

PHPBB3-11366
[ticket/11366] Correct a sentence

PHPBB3-11366
[ticket/11366] Coding style

PHPBB3-11366
[ticket/11366] Remove the double spaces

PHPBB3-11366
[ticket/11366] Fix detailed view

PHPBB3-11366
[ticket/11366] Align language strings

PHPBB3-11366
[ticket/11366] Update var names

PHPBB3-11366
[ticket/11366] Update FILE_NOT_FOUND language string

This var is always used with a colon.

PHPBB3-11366
[ticket/11366] Fix whitespaces

PHPBB3-11366
[ticket/11366] Update FILE_NOT_FOUND language string

PHPBB3-11366
[ticket/11366] Force the use of the cache on the list page

PHPBB3-11366
[ticket/11366] Add recheck-all link

PHPBB3-11366
[ticket/11366] Use force_cache on the list page

PHPBB3-11366
[ticket/11366] Add $config['extension_force_unstable']

PHPBB3-11366
[ticket/11366] Move "recheck all" link

PHPBB3-11366