Refactor yas-good-grace error handling

* yasnippet.el
(yas--handle-error): New function.
(yas--eval-lisp-no-saves, yas--eval-lisp): Use it.
Don't lose error message when yas-good-grace is t

* yasnippet.el
  (yas--eval-lisp-no-saves): Pass error message to message function.
  (yas--handle-error): Pass "%s" to error to avoid accidentally
  interpreting % in the error message as format codes.
Remove type, expand-env from new snippet value

They are seldom used, and can cause errors if left in.

* yasnippet.el (yas-new-snippet-default): Remove type and expand-env
  directives.
Restore backquotes lost in rst -> org translation

* doc/snippet-development.org: Re-add lost `s.
Document uuid directive

* doc/snippet-development.org: Mention uuid in directive list.
* yasnippet.el (yas-define-snippets): Fix docstring grammar.
Document type directive

* doc/snippet-development.org: Add type to directive list.