Get :defer-install completely working, in theory

Get :defer-install completely working, in theory

* A quoting error has been fixed in `use-package-handler/:defer'.
* `use-package-install-deferred-package' has been updated to return t
  if the package was actually installed, and nil otherwise.
* The fake autoloads generated during deferred installation are
  doctored so Emacs does not think they were defined in the user's
  init-file.
* The docstrings of the fake autoloads have been improved.
* Arguments and interactivity are now correctly passed to the
  autoloaded function.
* The autoload now skips requiring the feature and calling the
  original function if the user declines to install the package. This
  prevents unprofessional errors.