We should rethink is_outlier

[Shians]

So a few people have told me is_outlier is confusing for two reasons:

1. When we plot it TRUE actually implies a cell a filtered out, people tend to associate TRUE with GOOD and so when they see a low TRUE number they panic for a second. Maybe we should just rename it "not_outlier"

2. The is_outlier column is currently encoded as a factor, I know the reason is probably because that's how you get it to show up in the upper triangle of the ggpairs, but it makes a lot more sense to just encode it as a logical and create a temporary object with conversion to factors just before we call ggpairs.