[Merge] ~ddstreet/software-properties:lp645404 into software-properties:ubuntu/master

[Dan Streetman]

> I don't like this commit, it makes it harder to read for basically no benefit:
>     move 'datadir' into kwargs, set default in SoftwareProperties
> 
> same for rootdir moving into kwargs in the next commit. kwargs should be
> avoided as much as humanely possible. It prevents a lot of static checks
> (especially type checks get harder, and I'd love to add some mypy annotations
> at some point).
> 
> The removal of the Options stuff I don't like very much, I felt it was cleaner
> before.
> 
> 
> Refactoring of ShortCutHandler I can't really follow, it's too big.

Here's a different approach that makes the absolute minimum changes to SoftwareProperties, and splits up much of the rewriting to possibly be easier for you to review.

Just an initial draft, I need to go over the commits again and check the test updates, so it's not ready to merge yet but shoudl be ready for general review.
-- 
https://code.launchpad.net/~ddstreet/software-properties/+git/software-properties/+merge/367276
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