GitLab

* plstore.el: Add documentation.
(plstore-mode): New mode to edit plstore file.
(plstore-mode-toggle-display, plstore-mode-original)
(plstore-mode-decoded): New command.
(plstore--encode, plstore--decode, plstore--write-contents-functions)
(plstore--insert-buffer, plstore--make): New function.
(plstore-open, plstore-save): Simplify by using them.