Exports the value of a model checked property for all states as a vector.
If <file> is "stdout", this is displayed to the log instead of a file.
Currently, only works for a single property: if there is more than one,
then the file gets overwritten each time a property is checked.
Also fixes a bug in the underlying mechanism for storing results vectors
in the explicit engine (within Results objects).
When DOT graphs of a model are exported, their maximum permitted size is
hardcoded to 8 inches wide by 5 inches high, which is too small for the
rendered drawing to be useful (e.g. during debugging) for all but the
simplest of models. Remove the maximum size restriction, allowing tools
to render the drawing with its natural dimensions.
Dave Parker