fixed usage of wrong configuration set once the current menu item is not given
Merge branch 'v2.6.6'

Conflicts:
	site/views/event/view.html.php
	site/views/events/view.html.php
	site/views/singleimage/view.html.php
	site/views/singleimage/view.raw.php
added some checks to the install script so it does not throw exceptions
restores some Joomla 2.5 compatibility. It still looks kind of ugly but the J2.5 back end in general does :)