[ticket/12831] Optn to prevent setting HTTP headers

https://tracker.phpbb.com/browse/PHPBB3-12831

PHPBB3-12831
[ticket/12809] Fix select button and dropdown list items in RTL.

PHPBB3-12809
[ticket/12809] Remove obsolete rules and selector.

PHPBB3-12809
[ticket/12809] Restore text-align for the pagination.

PHPBB3-12809
[ticket/12822] Remove "None" option from avatar select boxes

This option is just used for deleting avatars for which we already have
a checkbox.

PHPBB3-12822
[ticket/12822] Add method for deleting avatars and use confirm_box

The method will take care of the actual deletion process in the avatar manager.
Additionally, we'll be using a confirm box while deleting the avatar to prevent
users from accidentally deleting their avatars.

PHPBB3-12822
[ticket/12822] Fix test runs of avatar manager_test

PHPBB3-12822
[ticket/12671] Possibility to use NOT LIKE expression

PHPBB3-12671
[ticket/12794] Properly validate google+ field against valid character set

PHPBB3-12794
[ticket/12671] Possibility to use NOT LIKE expression

PHPBB3-12671
[ticket/12671] Possibility to use NOT LIKE expression

PHPBB3-12671
[ticket/12671] Possibility to use NOT LIKE expression

PHPBB3-12671
[ticket/12951] Added editorconfig

PHPBB3-12951
[ticket/12671] Possibility to use NOT LIKE expression

PHPBB3-12671
[ticket/12831] reimplemented headers as array

https://tracker.phpbb.com/browse/PHPBB3-12831

PHPBB3-12831
[ticket/12831] simplified code, upd event block

https://tracker.phpbb.com/browse/PHPBB3-12831

PHPBB3-12831
[ticket/12956] Ensure the contact columns have been added before using them

PHPBB3-12956
[ticket/12831] fix CS

https://tracker.phpbb.com/browse/PHPBB3-12831

PHPBB3-12831
Merge pull request #2837 from Geolim4/ticket/12671

Ticket/12671 Possibility to use NOT LIKE expression

* Geolim4/ticket/12671:
  [ticket/12671] Possibility to use NOT LIKE expression
  [ticket/12671] Possibility to use NOT LIKE expression
  [ticket/12671] Possibility to use NOT LIKE expression
  [ticket/12671] Possibility to use NOT LIKE expression
  [ticket/12671] Possibility to use NOT LIKE expression
Merge pull request #2836 from marc1706/ticket/12794

[ticket/12794] Properly validate google+ field against valid character set

* marc1706/ticket/12794:
  [ticket/12794] Properly validate google+ field against valid character set