The method ``table.progress`` reports how many ``key_source`` entries have been populated and how many remain.
Two optional parameters allow more advanced use of the method.
A parameter of restriction conditions can be provided, specifying which entities to consider.
A Boolean parameter ``display`` (default is ``True``) allows disabling the output, such that the numbers of remaining and total entities are returned but not printed.

Move Python content to lang-spec file in Progress.
Move Python content to lang-spec file in Progress.
