DMV-21 error handling in IFileStore for exists() and lastChanged*()

...ystemsx/cisd/datamover/filesystem/intf/BooleanStatus.java

...h/systemsx/cisd/datamover/filesystem/intf/IFileStore.java

...systemsx/cisd/datamover/filesystem/intf/NumberStatus.java

...systemsx/cisd/datamover/filesystem/intf/ResultStatus.java

...cisd/datamover/filesystem/remote/CopyActivityMonitor.java

...temsx/cisd/datamover/filesystem/store/FileStoreLocal.java

...emsx/cisd/datamover/filesystem/store/FileStoreRemote.java

...sd/datamover/filesystem/store/FileStoreRemoteMounted.java

.../systemsx/cisd/datamover/utils/QuietPeriodFileFilter.java

.../datamover/filesystem/remote/CopyActivityMonitorTest.java

...temsx/cisd/datamover/utils/QuietPeriodFileFilterTest.java