Refactoring, changes here and there

* dankrusi: Added changelog file
* dankrusi: Changed output/build directory
* dankrusi: Refactored panel ui code from MenuButton to PanelWindow (simplifies new features)
* dankrusi: Added border in edit mode of panel items
* dankrusi: Single menu window
* dankrusi: Panel item dialog window title
* dankrusi: Refactored simulation to seperate connection class (needs to be finished)