[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/12535] Make <a> adjust to the image width

PHPBB3-12535
[ticket/12535] Add events to subsilver2

Forgot subsilver... yet again

PHPBB3-12535
Merge remote-tracking branch 'origin/ticket/10472' into test/all
Merge remote-tracking branch 'origin/ticket/12408' into test/all
Merge remote-tracking branch 'origin/ticket/12535' into test/all
Merge remote-tracking branch 'origin/ticket/12559' into test/all