#1: Consistent implementation for attribute "centercoords" (Getter and Setter)

* Renamed internal method __centercoords() to __getCentercoords()
* Implementend new setter __setCentercoords()
#1: Consistent implementation for attribute "monitorID" (Getter and Setter)

* Renamed internal method __monitorID() to __getMonitorID()
* Implementend new setter __setMonitorID()
* new membervariable __useEventHook to be able to disable Evenz-Hooking for debbuging purposes
#1: Adapted main program to reflect replacing functions with attributes (maximize() -> maximized := 1)
Changed icons for minimize and maximize action
Merge branch 'feature/#1' into develop