Create missing users in phpBB3 and improve usability

Improve usability: Cleaner look
Improve usability: Don't show unused configuration parameters
Improve usability: Select all import options by default
Improve usability: Truncate selected tables before import
Improve usability: Unselect already imported tasks
Improve usability: Changing configuration options should have effect when clicking "Import" or "Truncate"
phpBB3 support: Fix various issues with user import
phpBB3 and SMF2 support: allow user to create new Joomla users
Improve usability: Nice startup screen with cool icons & instructions
Add initial support for deprecated phpBB2 (#37)

Kunena / com_kunenaimporter