add ability to download AO3 workskin if scraping styles is enabled

[niacdoial]

If the "keep_html_attrs" config parameter includes "style", add the workskin (for AO3 works that have one) to the ebook's stylesheet.

[JimmXinu]

I'd like a few changes before accepting this:

1. This should be a new configuration switch such as use_workskin. Inclusion of style in keep_html_attrs shouldn't be the controlling element. If anything, an author using inline styles probably indicates they don't use workskin CSS.

   Search for use_view_full_work in fanficfare/configurable.py (in two places), fanficfare/defaults.ini, and calibre-plugin/plugin-defaults.ini for examples of what to add where.

2. I'd appreciate comments in story.py and base_writer.py about extra_css that refer to the new setting.

3. FFF is still back compatible to old versions of Calibre in python2. Please use from ..six import text_type as unicode and unicode instead of str for consistency.

[niacdoial]

1. OK, I will do that. Should that new option be false by default ?
2. OK.
3. ... I feel like I should have thought of it myself, oh well.

[JimmXinu]

1. Yes. Commented out and false is what we usually do. Thanks.

[niacdoial]

done! I also spotted while searching that AO3 was not the only site to use use_view_full_work

[niacdoial]

thanks!

[JimmXinu]

That pointed out to me that squidgeworld also shares all settings with AO3, so I made some more lists.

However, while testing this, it occurs that the CSS order should be workskin, then output_css setting so user can override workskin in personal.ini.

[niacdoial]

oh. well, I got a new commit out that fixes that, if you didn't do so on your side yet

[chocolatechipcats]

@niacdoial just wanted to thank you personally for letting me download a story that had tricky CSS that I couldn't get working manually!