Merge pull request #22 from Wohlstand/master

Merge to Update 22
Add some work to redo!
Merge pull request #23 from Wohlstand/master

Merge to Update 23
Merge branch 'master' of https://github.com/KevinW1998/PlatGEnWohl.git
Improve redo function and implement undo/redo for gui --> now working with remove!
Merge pull request #16 from KevinW1998/master

Implement now first working operation with undo/redo: remove-operation