[ticket/12563] Changes 2 language variables to better understandable names

PHPBB3-12563
[ticket/12563] Removes strintf in acp_styles.php and shorts up <a>

PHPBB3-12563
[ticket/12563] Removes ending . from <a>

PHPBB3-12563
[ticket/12728] Enforce box model sizing on image attachment thumbnails

PHPBB3-12728
[ticket/12728] Adjust .postimage sizing to 100%

PHPBB3-12728
[ticket/12690] Add core.submit_pm_after event

Add core.submit_pm_after to funtion submit_pm.
Event will return just submited msg_id. It should be plased
just before return $data['msg_id'];

Justification:
Using only core.submit_pm_before does not allow to
follow up after message submission.
The message ID is recieved at DB submission.
Some times we need the MSG_ID as identifier

PHPBB3-12690
[ticket/12690] Add other info to core.submit_pm_after

Added $mode
Added $subject
Added $data
Added $pm_data

PHPBB3-12690
[ticket/12690] Remove $msg_id and chmod

Remove inneded $msg_id
Chmod file to 644

PHPBB3-12690
[ticket/12696] Add events to ucp_register.html

Add events to UCP Register template:
ucp_register_before - add before start of registration form fields
ucp_register_after - add after end of registration form fileds
ucp_register_passowrd_after - add event after passowrd field
ucp_register_language_before - add event before language selector
ucp_register_profiles_before - add event just before begining of
registration profile informatiom

All events are inside the registration form fieldset.
All events are inside the registration form

Justification:

Add abbility of extension author to include custom
checks or fields inside the registration form.
Like age check field/verification.

PHPBB3-12696
[ticket/12696] Add prosilver ucp_register

Add events to prosilver ucp_register

PHPBB3-12696
[ticket/12696] Add events to evets.md

Add events in documentation

PHPBB3-12696
[ticket/12696] A small error with events.md perms

docs/events.md was in 755 changed to 644

PHPBB3-12696
[ticket/12696] Naming convention changes

Some changes propsed by nickvergessen

PHPBB3-12696
[ticket/11528] Add behat/mink and mink-goutte-driver as dependency

PHPBB3-11528
[ticket/11528] Refactor install_board() code into a new class

PHPBB3-11528
[ticket/11528] Instantiate $client, $driver from functional test case

Make mink test case an abstract class, instantiate $driver, $client
from its child class i.e. functional test case.

PHPBB3-11528
[ticket/11528] Call parent::tearDown in overrided tearDown method

PHPBB3-11528
[ticket/11528] Move parent::tearDown() to end of tearDown()

PHPBB3-11528
[ticket/11528] Use 'use' keyword to import classes to current scope

PHPBB3-11528
[ticket/11528] Add asserts in installation steps

PHPBB3-11528