Random tweaks:

 - change click-by-click advice on modifying saved sessions
 - add `Restart Session' as another reason you might not want to close the
   window on exit; other tweaks to this language
 - mention Shift-Backspace action
 - the window resizing configuration documentation was completely out of
   date; rewrite
 - add a note about Default Bold Background since it's caused confusion
 - "remote terminal" -> "remote system" in terminal-type doc

git-svn-id: svn://svn.tartarus.org/sgt/putty@4686 cda61777-01e9-0310-a592-d414129be87e