TextEdit: add line based deletes

TextEdit: add line based deletes

this allows a bash/emacs like keybindings:
 <bind context='textentry' action='cursor-begin' key='Ctrl-a'/>
 <bind context='textentry' action='cursor-end' key='Ctrl-e'/>
 <bind context='textentry' action='cursor-left-word' key='Alt-b'/>
 <bind context='textentry' action='cursor-right-word' key='Alt-f'/>
 <bind context='textentry' action='delete-char' key='Ctrl-d'/>
 <bind context='textentry' action='delete-line-begin' key='Ctrl-u'/>
 <bind context='textentry' action='delete-line-end' key='Ctrl-k'/>
 <bind context='textentry' action='delete-word-end' key='Alt-d'/>
 <bind context='textentry' action='delete-word-begin' key='Ctrl-w'/>

BTW: Some default bindings (eg Ctrl-Left) won't work on most terminals