correct handling of initial attribute value

...bmotionstudio/gef/editor/attribute/AbstractAttribute.java

...ditor/src/de/bmotionstudio/gef/editor/model/BControl.java

...tor/observer/wizard/WizardObserverCSwitchCoordinates.java

...rver/wizard/WizardObserverListenOperationByPredicate.java

...ef/editor/observer/wizard/WizardObserverSetAttribute.java

...itor/observer/wizard/WizardObserverSwitchCoordinates.java

...gef/editor/observer/wizard/WizardObserverSwitchImage.java