Fix external runtime problem parameter count

Add getProblemDimension method to ExternalRuntimeProblem so that
problem dimension is not overridden from inherited method.

src/main/java/eva2/problems/ExternalRuntimeProblem.java

@@ -363,6 +363,10 @@ public class ExternalRuntimeProblem extends AbstractOptimizationProblem
         this.initializationRange.adaptRowCount(t);
     }
 
+    public int getProblemDimension() {
+        return this.problemDimension;
+    }
+
     /**
      * Length of the x vector at is to be optimized
      *