Feature request #573: REQUEST: Interface for numeric adjustment of ratings (0-100)

Opening this feature request as a follow-up to feature request #240. That request originally asked for a way of setting half-star ratings from the menu, and that's now been implemented.

But something else that came up in the discussion was the ability to set any numeric rating in the range of 0 to 100 using a dialog (see https://wincent.dev/a/support/bugs/show_bug.cgi?id=240#c3), so I am opening this request to track that feature separately.

I actually started implementing that dialog -- it would be fairly easy to add -- but realized that it may actually be better to roll this functionality into an "Inspector" dialog that allows you to set more than just the rating. So I'm going to leave this issue open for comments while I decide what to do.