[This is preliminary documentation and subject to change.]
Returns whether the loading process has been terminated, i.e. all loading should stop.
All loading code should periodically (e.g. between loading each file) check this and exit as soon as it is seen to be true.
Reading this property implicitly causes the WatchdogToken to be pinged, informing the WatchdogProcess that the loader is still responsive. Therefore the remarks about the Ping method apply to this property regarding when it should and should not be used.