[ticket/12408] Add quick setting for "default guest style" to ACP

PHPBB3-12408
[ticket/12408] Simplified queries

PHPBB3-12408
[ticket/12408] Code cleanup

Rebased to see if travis will finally play along

PHPBB3-12408
[ticket/12408] Public functions and updated doc block

PHPBB3-12408
[ticket/12408] Changed lang vars, added fieldset and removed "default"

PHPBB3-12408
[ticket/10472] Fix ACP overflow:hidden problem for medium-sized screens

PHPBB3-10472
[ticket/10472] More clearing and white-space fixes

PHPBB3-10472
[ticket/10472] Fix weird padding on input type=number

PHPBB3-10472
[ticket/12961] Add link in anti-spam ACP page to titania

PHPBB3-12961
[ticket/12961] Change url to https://www.phpbb.com/go/anti-spam/

PHPBB3-12961
[ticket/12961] Change url to anti-spam-ext

As per IRC suggestion

PHPBB3-12961
[ticket/12961] Refactor lang entry

PHPBB3-12961
[ticket/12961] Move link to language file

PHPBB3-12961
[ticket/12961] Add additional link to the KB

PHPBB3-12961
[ticket/12559] Add forum setting to limit subforum legend

Squashed all commits, they were basically just typos and errors

PHPBB3-12559
[ticket/12559] Applied DeMorgan and removed unnecessary true:false

PHPBB3-12559
[ticket/12559] Updated copyright information

PHPBB3-12559
[ticket/12961] Remove target="_blank" and switch to <strong>

PHPBB3-12961
[ticket/12961] Fix missing phpBB.com

Don't know how that happened. Weird

PHPBB3-12961
[ticket/12598] Improve search box styling

PHPBB3-12598