(Single Shell): Replace uudecode example with gpg example.

(Single Shell): Replace uudecode example with gpg example.
Document async shell commands.
(Shell History): Clarify.
(Shell Ring): Mention C-UP an C-DOWN.
(Shell Options): Add comint-prompt-read-only.
(Invoking emacsclient): Set EDITOR to run Emacs.
(Sorting): No need to explain what region is.
(Saving Emacs Sessions): Fix typo.
(Recursive Edit): Fix punctuation.
(Emulation): Don't mention "PC bindings" which are standard.
(Hyperlinking): Explain Mouse-1 convention here.
(Find Func): Node deleted.