supybot-plugin-create: use options.desc to fill in more fields, saner defaults

- `options.desc` will now fill in the part used by `plugin help`.
- Remove the `Insert a more detailed description of your plugin here` part from `README.md`. Since the wizard already requires a description, it's useless to *still* add a placeholder.
- Don't escape apostrophes in `__init__.py`'s comments; we're already using docstring quotes, so this is not needed.