In any proceeding before any general district court a defendant may, at his option, at any time before trial, plead in writing as a counterclaim, any cause of action at law for a money judgment in personam, or any matter which would entitle him to relief in equity in the nature of damages, that he has against the plaintiff or all plaintiffs jointly, whether or not it grows out of any transaction mentioned in the warrant or notice of motion for judgment, whether or not it is for liquidated damages, whether or not it is in tort or contract, and whether or not the amount demanded exceeds the amount claimed by the plaintiff in the warrant or notice of motion for judgment; however, no such counterclaim shall be filed or heard when the amount claimed therein exceeds the amount within the jurisdiction of such court. Upon the request of either party, bills of particulars and grounds of defense may be ordered to ensure a fair trial on the merits of the issue presented. The court may, in its discretion, hear the counterclaim together with the original case, or may order and hold a separate hearing of any cause of action asserted in a counterclaim. In either event, the court shall render such final judgment on the whole case as the law and the evidence require.