make the help menu shortcut display more flexible, add more intuitive

make the help menu shortcut display more flexible, add more intuitive
aliases for moving to the beginning and end of a paragraph and
justifying the entire file, and make those aliases available in the main
shortcut list too, since Pico's practice of putting them in the search
menu is rather odd

git-svn-id: svn://svn.savannah.gnu.org/nano/trunk/nano@1934 35c25a1d-7b9e-4130-9fde-d3aeb78583b8