UI: Fix the the mousewheel scrolling in the left panel

Before this fix, scrolling with the mouse wheel was working only when the
cursor was over a component. Now it doesn't matter, as long as the cursor is
in the ScrollView
Remove unused StablexUI xml files
Import of the second dungeon algorithm

Port of the dungeon generator originally written by Alexander Fast
see https://github.com/mizipzor/roguelike-dungeon-generator
Updating UI and DungeonManager for the second dungeon algorithm
MiscDungeonWrapper: remove unused empty method