The court may reserve jurisdiction to modify a final decree for alimony only under the following conditions: where there is no jury trial as to the issues in question: andthe issues were settled by an agreement which was incorporated into the final decree and made the judgment of the court; andthe agreement as incorporated reserved jurisdiction in the court to modify the terms of the decree in question. The above procedure was the only method by which a decree could be modified until the passage of the 1955 act provided a statutory procedure...