Added spacing between matrix rows.

src/main/java/de/monticore/lang/monticar/mpp/montimath/TeXMathPrettyPrinter.java

@@ -41,7 +41,7 @@ public class TeXMathPrettyPrinter extends MathPrettyPrinter implements TeXMathSt
     @Override
     public void visit(ASTDivideExpression node) {
         this.needsParenthesis = false;
-        this.printer.print("\\frac{");
+        this.printer.print("\\dfrac{");
     }
 
     @Override
@@ -94,7 +94,7 @@ public class TeXMathPrettyPrinter extends MathPrettyPrinter implements TeXMathSt
 
     @Override
     public void revisit(ASTMathMatrixValueExplicitExpression node) {
-        this.printer.print("\\\\");
+        this.printer.print("\\\\\\\\");
     }
 
     @Override