Replace phpBB Group with phpBB Limited

EXTTOOLS-654

- "phpBB Group" replaced with "phpBB Limited"
Replace phpBB Group with phpBB Limited

EXTTOOLS-654

- Update: "style.css" header based on phpBB "stylesheet.css" header
"http://www.phpbb.com" replaced with "https://www.phpbb.com"

EXTTOOLS-654
Fix header indentation

EXTTOOLS-654
Merge pull request #34 from phpbb-fr-com/qi-exttools-654

Quickinstall: exttools 654