Add two new listbox related method to get the first page and the last page of...

Add two new listbox related method to get the first page and the last page of a multiple-page listbox.
Auto-delete of trailing spaces.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@8679 20353a03-c40f-0410-a6d1-a30d3c3de9de