Add a script which generates using JSGF and parses with GF

[Kaljurand]

This script could be used in testing to make sure that no unwanted (or avoidable) approximation has occurred during the GF->JSGF conversion.

The script should highlight phrases which are accepted by the JSGF but not by the original GF grammar. We know that approximation happens during JSGF->FSA, but maybe it happens already during GF->JSGF in which case it can probably be avoided by redesigning the grammar.