code: function(packageName, version) {
              Ext.versions[packageName] = new Version(version);
              Ext.lastRegisteredVersion = Ext.versions[packageName];
  
              return this;
          }
docs: Set version number for the given package name.
  
  @param {String} packageName The package name, for example: 'core', 'touch', 'extjs'
  @param {String/Ext.Version} version The version, for example: '1.2.3alpha', '2.4.0-dev'
  @return {Ext}