[Plugin] PunctuationSmarten Sigil plugin

[DiapDealer]

OK. I'm going to post a new version of the plugin to test. It has been completely rewritten using Qt for Python rather than tk/tkinter.

Functionally, this test version should work exactly like the old version. I'm just looking to verify that everything works like it always did. New stuff will have to wait.

There's a lot of extra debug output that could come in handy if anyone runs into complications.

As always, make good backups and create lots of checkpoints with Sigil to help make sure nothing is happening that shouldn't be.

I don't expect trouble, but be smart about testing.

EDIT: in case it wasn't obvious, this new version is not going to work with anything less than Sigil 2.0 (and nothing less than Python 3.6 if you're using an external Python interpreter for plugins).