Documentation update
Add empty index.php files to all directories
Small fixes
Some more small tweaks

* Tested up to WP 3.8-beta
* Removed auto-deactivation
* Removed some backward compatibility for old WP versions
* Now using get_admin_page_title() and screen_icon()
* Move creating of table row with select box to separate method
Grr.. index.php files need php opening tags for code sniff validation
API documentation (actions/filter)
Updated translation files