Tidyup 8 - Expanding the filter() family (#30)

* Tidyup 008 - Retaining and excluding rows

* Add tables

* Use a logical for `deceased`

* Add a `name` column for easier row tracking

* Tweak the SQL header name

* Change `.combine` to `.when`

* Fix typo

* Talk about `%in%`

* Drop `.missing` and talk about why it's a red herring

* Replace `when_any/all()`'s 3-valued `missing =` with binary `na_rm =`

* Mention `data |> exclude(this | that | those)`

* Revert "Mention `data |> exclude(this | that | those)`"

This reverts commit cff71bc.

* Rework `%in%` example

* Mention `union()` invariant

* Rework around `filter_out()`

* Accepted

Author: DavisVaughan