[selectors] match_kwargs and match_form_params selectors both accept a new `once_is_enough` argument (closes #1990438)
also fix docstring of match_exception and references to selectors in the book.
sync_schema_props_perms('state_of')
sync_schema_props_perms('transition_of')
for etype in ('State', 'BaseTransition', 'Transition', 'WorkflowTransition'):
sync_schema_props_perms((etype, 'name', 'String'))