Reworked top-level element treatment

...g/fortiss/tooling/kernel/interfaces/IStorageProvider.java

...ing/kernel/interfaces/ITopLevelElementChangeListener.java

...ss/tooling/kernel/interfaces/ITopLevelElementContext.java

...rc/org/fortiss/tooling/kernel/internal/ActionService.java

.../fortiss/tooling/kernel/internal/CommandStackService.java

...org/fortiss/tooling/kernel/internal/NavigatorService.java

...g/fortiss/tooling/kernel/internal/PersistencyService.java

...rnel/internal/navigator/NavigatorTreeContentProvider.java

.../tooling/kernel/internal/navigator/NavigatorViewPart.java

.../kernel/internal/properties/PropertiesAdapterFactory.java

...ernal/storage/eclipse/EclipseResourceStorageProvider.java

...tooling/kernel/internal/storage/eclipse/ModelContext.java

...c/org/fortiss/tooling/kernel/services/IActionService.java

...rg/fortiss/tooling/kernel/services/INavigatorService.java

.../fortiss/tooling/kernel/services/IPersistencyService.java

...rg/fortiss/tooling/kernel/util/EObjectSelectionUtils.java

.../fortiss/tooling/kernel/util/ProjectRootElementUtils.java