Code review comment for ~ddstreet/software-properties:lp645404

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.