Moved showPrevButton to tour step
Update package.xml

Resetting update instructions. Setting version to 0.5.0
Merge branch 'master' into tour_step/options

Conflicts:
	files/lib/acp/form/TourAddForm.class.php
	files/lib/acp/form/TourEditForm.class.php
	lang/de.xml
Merge pull request #20 from MeinAccount/tour_step/options

Moved showPrevButton to tour step