[LMS-2379] - Allow to delete a dataset even if it's not on the file system

...msx/cisd/openbis/dss/generic/server/DataStoreService.java

...sd/openbis/dss/generic/server/DataStoreServiceLogger.java

...enbis/generic/client/web/client/ICommonClientService.java

.../generic/client/web/client/ICommonClientServiceAsync.java

...d/openbis/generic/client/web/client/application/Dict.java

...cation/ui/data/DataSetListDeletionConfirmationDialog.java

...ient/web/client/application/ui/deletion/DeletionGrid.java

.../client/application/ui/deletion/EmptyTrashButtonMenu.java

...application/ui/deletion/EmptyTrashConfirmationDialog.java

...ui/widget/AbstractDataListDeletionConfirmationDialog.java

...penbis/generic/client/web/server/CommonClientService.java

...ch/systemsx/cisd/openbis/generic/server/CommonServer.java

...temsx/cisd/openbis/generic/server/CommonServerLogger.java

...cisd/openbis/generic/server/business/bo/DataSetTable.java

...enbis/generic/server/business/bo/DeletedDataSetTable.java

...isd/openbis/generic/server/business/bo/IDataSetTable.java

...nbis/generic/server/business/bo/IDeletedDataSetTable.java

.../generic/server/plugin/IDataSetTypeSlaveServerPlugin.java

...h/systemsx/cisd/openbis/generic/shared/ICommonServer.java

...stemsx/cisd/openbis/generic/shared/IDataStoreService.java