[ticket/10155] Update jQuery to 1.8.3

Currently included jQuery is old by now, v1.6.2. We should update to
1.8.3. This allows us to take advantage of the latest form of jQuery
event delegation ($.on). I don't think it wise to update to jQuery
1.9.x yet, as many 3rd party scripts still need to be updated to cope
with its deprecated features ($.browser). Therefor, 1.8.3 is the latest
and most widely compatible stable version right now.

PHPBB3-10155
[ticket/10155] Use new migration file for jQuery config update
[ticket/10155] Use more descriptive title for migration file

PHPBB3-10155
[ticket/10155] Make effectively installed test more specific

PHPBB3-10155
[ticket/10325] add allow forgot password option in acp

PHPBB3-10325
[ticket/10325] trigger error if forgot password option disabled

PHPBB3-10325
[ticket/10325] add new config value to database

PHPBB3-10325
[ticket/10325] fix language

PHPBB3-10325
[ticket/10325] change language var

PHPBB3-10325
[ticket/10325] fix language variable

PHPBB3-10325
[ticket/10325] fix language key

PHPBB3-10325
[ticket/10325] improve acp option language

PHPBB3-10325
[ticket/10325] fix language in acp and ucp

PHPBB3-10325
[ticket/10325] add logout function in functional_test_case

PHPBB3-10325
[ticket/10325] functional tests for forgot password functionality

PHPBB3-10325
[ticket/11442] Use correct button class for ajaxified confirm_box

In commit 001572f the HTML code for the ajaxified confirm_box was moved
from overall_footer.html to confirm_body.html. While copying, the CSS
class of the "Yes" button was changed from button1 to button2. Due to the
fact that the phpbb.confirm() method uses the class button1 to check if
"Yes" was clicked, this broke the ajaxified confirm box in the ACP. With
this small patch the confirm boxes in the ACP should work properly again.

PHPBB3-11442
[ticket/10325] add assert_response_success in test

PHPBB3-10325
[ticket/10325] fix language in acp and ucp

PHPBB3-10325
[ticket/10325] use assert_response_success parts

PHPBB3-10325
[ticket/11435] Fit comment into 80 columns and link to php manual.

PHPBB3-11435