[EMACS]use desktop(built-in) and bookmark-plus for session management

1. remove desktop-menu.el, have some issues setting it up on osx
2. install bookmark+ from elpa
3. set up desktop functions
4. remove desktop-menu settings in clutter.el

http://www.emacswiki.org/BookmarkPlus
http://www.emacswiki.org/emacs/DeskTop