[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/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/12559] Updated copyright information

PHPBB3-12559
[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/12506] Reposition post-buttons for compact layout

PHPBB3-12506
[ticket/12506] Reposition buttons to make room for "online" banner

PHPBB3-12506
[ticket/12506] Fix responsive profile min-height (no avatar)

PHPBB3-12506
[ticket/12506] Fix search result h3 margin

There are no buttons present, so don't need to do all this stuff.

PHPBB3-12506
[ticket/12598] Improve search box styling

PHPBB3-12598
[ticket/12598] Add lt IE9 fixes

In case this one gets merged before hanakin's gradient PR.

PHPBB3-12598
[ticket/12598] Remove unused link colors

PHPBB3-12598
[ticket/12598] Clean up unused link colors

PHPBB3-12598
[ticket/12598] Add some responsive margin to give breathing room

PHPBB3-12598