Added new setting: bypassShopInteractionBlocking (default: false) (not
yet used)
Renamed setting: deletingPlayerShopReturnsEgg ->
deletingPlayerShopReturnsCreationItem
Also renaming the previously renamed setting in the default config file.
Started restructuring: Tried to separate things into additional classes,
especially move things out of the main plugin class and make some things
slightly more abstract:
* all living shopkeeper types share one listener now
* made the shopkeeper types more abstract
* made the shop object types more abstract
* tried to make the user interface stuff (trading, hiring, editor
windows) more abstract (though, I am not quite sure yet if that was an
improvement..)
* many more tiny changes everywhere..

Work in progress.
New Files which were somehow missing in the previous commit.
Shading the apache commons collection libary in.
Removed the new introduced apache collections dependecy again and
replaced the LinkedMap with a linear search (which shouldn't have any
impact for our very few entry we need iterate through).
Fixes for issues introduced in the previous refactoring.
Did some tiny renaming: 'interface' -> 'interface window' or similar
(Re-)Added missing shopkeeper inventory closing, when an editor window
is closed. I think this went lost during the previous restructuring.
Fixed tiny typo.
Removed unused import.