Merge pull request #12 from KevinW1998/master

Adding cut function + paste improve
Fixed disabled animation state
Added CUT action in MainWindow's menu
Fixed style bugs for Linux and Mac OS on DoorBox
Moved levelscene class files into own folder
Add group selected context menu for BGO
Copy/cut items in Block's context menu
Added HistoryManager by Kevsoft
Update .gitignore
Small code optimizing
added NPC indexes. added BugProtectors in WriteFile
NPC class template
Protector for non-animated items
Added Change Layer menu
Small changes
NPC item index
Merge pull request #18 from Wohlstand/master

Merge to Update 18