Refactor to make CellSample class more self-contained

src/main/java/InteractiveInterface.java

@@ -74,7 +74,7 @@ public class InteractiveInterface {
             System.out.println(ex);
             sc.next();
         }
-        CellSample sample = Simulator.generateCellSample(numCells, cdr1Freq);
+        CellSample sample = new CellSample(numCells, cdr1Freq);
         assert filename != null;
         System.out.println("Writing cells to file");
         CellFileWriter writer = new CellFileWriter(filename, sample);