modified the interface for toolbarItems so that the reference to the backend Object...

modified the interface for toolbarItems so that the reference to the backend Object in the constructor is optional, this was necessary to have AJAX response methods in the same class as the code that generates the toolbar item itself

git-svn-id: https://svn.typo3.org/TYPO3v4/Core/trunk@3242 709f56b5-9817-0410-a4d7-c38de5d9e867