Adds the '!prev' command to the CUI

src/mohawk/MohawkCUI.java

 package mohawk;
 
 import java.io.*;
-import java.util.ArrayList;
-import java.util.Scanner;
+import java.util.*;
 
 import org.apache.commons.cli.Options;
 
 public class MohawkCUI {
     public static String previousCommandFilename = "MohawkCUIPreviousCommand.txt";
+    public static String previousCmd;
 
     public static void main(String[] args) {
         MohawkInstance inst = new MohawkInstance();
@@ -48,17 +48,25 @@ public class MohawkCUI {
             if (cmd.equals("!exit")) {
                 break;
             }
+
+            if (cmd.equals("!prev")) {
+                argv.clear();
+                argv.addAll(Arrays.asList(previousCmd.split(" ")));
+                break;
+            }
             argv.add(cmd);
         }
         user_input.close();
 
         System.out.println("Commands: " + argv);
 
-        FileWriter fw;
         try {
-            fw = new FileWriter(previousCommandFilename, false);
-            fw.write(fullCommand.toString());
-            fw.close();
+            if (!cmd.equals("!prev")) {
+                FileWriter fw;
+                fw = new FileWriter(previousCommandFilename, false);
+                fw.write(fullCommand.toString());
+                fw.close();
+            }
         } catch (IOException e) {
             System.out.println("[ERROR] Unable to write out previous command to: " + previousCommandFilename);
         }
@@ -86,12 +94,13 @@ public class MohawkCUI {
         System.out.println("-mode bmc -run all -bulk -input data/testcases/mixed !exit");
         System.out.println("");
         System.out.println("-mode bmc -run all -input data/ahn/test.st.mohawk.T.mohawk !exit");
+        System.out.println("-mode bmc -run all -input data/bug/isolation/ -skiprefine -bulk !exit");
         System.out.println("");
         try {
             BufferedReader bfr = new BufferedReader(new FileReader(previousCommandFilename));
-            String previousCmd = bfr.readLine();
+            previousCmd = bfr.readLine();
             bfr.close();
-            System.out.println("Previous Command: " + previousCmd);
+            System.out.println("Previous Command ('!prev' to use the previous command): " + previousCmd);
         } catch (IOException e) {
             System.out.println("[ERROR] Unable to load previous command!");
         }