DevTools: Move jsdifflib to "sources", extract "toolbox" module

Source/devtools/front_end/sources/jsdifflib.js

 /*
  * This is part of jsdifflib v1.0. <http://snowtide.com/jsdifflib>
  *
  * Copyright (c) 2007, Snowtide Informatics Systems, Inc.
  * All rights reserved.
  * 
  * Redistribution and use in source and binary forms, with or without modification,
  * are permitted provided that the following conditions are met:
  * 
  *    * Redistributions of source code must retain the above copyright notice, this
@@ skipping 389 matching lines @@
             var la = this.a.length;
             var lb = this.b.length;
             return _calculate_ratio(Math.min(la, lb), la + lb);
         }
 
         this.isjunk = isjunk ? isjunk : difflib.defaultJunkFunction;
         this.a = this.b = null;
         this.set_seqs(a, b);
     }
 }